Based on Richard Hooker’s novel and directed by Robert Altman, doctors at a field hospital during the Korean War perform bloody surgeries and try to adapt to their situation with humor and fellowship.
In Korea during the war at a base camp Hawkeye Pierce (Donald Sutherland) put his things in a jeep and is told that just because he is a captain does not mean he runs things. A black soldier tells him he runs it and that a driver will be with him soon. A truck parks nearby, and Captain Duke Forrest (Tom Skerritt) asks if this is 4077th MASH. Hawkeye says this is the jeep, and Duke gets in and tells him to go. Hawkeye gets in and drives off. The black soldier sends military police after a man says they just stole his jeep. They hear a bang, and the military police’s jeep stops. The black soldier fights with them.
The other jeep drives to a camp with large tents. Duke invites Hawkeye to go in and get a sandwich for lunch with him. Three soldiers wonder who they are. The two new guys sit with attractive women, and Duke says he thinks he is in love and asks her to show him around. Hawkeye advises him to notice the ring indicating she is married. Col. Henry Blake (Roger Bowen) says he is the commanding officer and goes over and asks if they are passing through. Duke calls her “Dish” (Jo Ann Plug). Blake says she is a lieutenant, and he is a colonel. Duke introduces himself and his driver, but Hawkeye says he is a captain too. Dish shakes hands with Hawkeye and leaves. Blake says he heard that Hawkeye stole a jeep, but Hawkeye says he did not because it is right out there. Blake reminds Duke that he is supposed to report to the commanding officer with his orders. Duke says he and Hawkeye were drinking all day. Blake says things will get busier. Hawkeye learns they have seventeen nurses there, and his unit will have four. Blake introduces Father John Mulcahy (Rene Auberjonois), Captain Waldowski (John Schuck), and John Black. Blake calls over Corporal “Radar” O’Reilly (Gary Burghoff) and tells him to change the numbers on that jeep.
Duke tries to pick up a woman who tells him to unhand her. They hear a young soldier reading the 23rd Psalm aloud slowly with Major Frank Burns (Robert Duvall) who tells them he is teaching him to read. Duke gives the youth a Playboy magazine to read, and he asks the major if he can leave now.
In the surgery tent doctors asks for sponges and talk to the nurses. Hawkeye uses a hacksaw and asks a nurse to scratch his nose.
In the sleeping tent the youth Ho-Jon (Kim Atwood) passes around martinis. Burns says he does not approve and kneels down and says the Lord’s prayer. The others say “Amen,” but Burns continues praying. Duke asks Burns how long this goes on, and he says he has to pray for their souls too now. The others sing “Onward Christian Soldiers” and march around the tent.
Col. Blake asks a nurse about the line-up. Hawkeye and Duke tell Blake he has to get Burns out of their tent. Blake says he won’t be intimidated. Hawkeye says they need to get a chest cutter in there. Blake says no MASH unit has a chest surgeon. He tells them they have to go to work early for a 12-hour day. Blake says that Burns will be out of their tent in 24 hours.
During surgery doctors call the priest “Dago” and tell him to hold things for them.
Ho-Jon is looking for Hawkeye, and he sees a sign on his sleeping tent “After hours CLOSED.” Inside Hawkeye is telling a nurse he is happily married as they caress each other. Ho-Jon knocks and calls his name. He says Duke wants him back quickly because they have a new chest cutter in their tent. Hawkeye puts on a coat, kisses her, and goes out.
Duke tells Hawkeye that he has been in the army two months. Trapper John McIntyre (Elliott Gould) says he worked in a hospital back home. They ask the name of the hospital. Hawkeye offers him a martini, and McIntyre asks if they use olives. They say they are near the front line and have to make accommodations.
In surgery McIntyre is operating. He tells a nurse it is good thing she has a good body, or they would get rid of her quickly.
Outside the tents McIntyre throws a football to Hawkeye. They see men peeking in the showers, and Hawkeye says Waldowski is the best equipped dentist.
A helicopter lands, and Major O’Houlihan (Sally Kellerman) gets out.
In surgery Burns asks a young soldier to get him a cardiac needle; but the kid comes back with the wrong needle, and Burns says he killed the patient. Blake introduces O’Houlihan as the new chief nurse. Blake takes her to the pre-op ward. McIntyre asks Burns if he is through for the day, and McIntyre says he wanted to make sure he has time sleep this off. Then he slugs him. Blake asks who started this, and McIntyre says Burns is an ignoramus. Burns says he did not have his guard up, and he wants him to let them settle this themselves alone. Blake says he is not running an English boarding school. Blake tells McIntyre that he is under arrest and is to confine himself to quarters pending an investigation. McIntyre asks if he is kidding. Blake tells them to try to remember that they are a military organization, and O’Houlihan agrees with him. Blake orders Sgt. Major Vollmer (David Arkin) to confine McIntyre to his quarters. McIntyre ignores Vollmer and leaves the tent.
McIntyre tells Blake he did not think Burns would get up. Duke and Hawkeye say that Burns is a medic and when anyone croaks, he blames it on someone else. This time he blamed it on a kid. Blake says he is tired of trying to run things for this outfit, and this time there is going to be disciplinary action. Blake says he was going to appoint McIntyre chief surgeon; but if he did that now, O’Houlihan would report it from Washington to Seoul. He asks if they have any sugar.
Blake is fishing in a stream, and a soldier reports to him that the general could not answer his call because he is at a football game. Blake says the generals have all the fun.
In the dining tent O’Houlihan asks Hawkeye if she can join him, and he says she already has. He asks where she is from, but she likes to think of the army as her home. She has been observing the nurses on his team, and he says he thinks they are just fine.
The lights go out in surgery, and Radar shines a bright flashlight.
O’Houlihan says that Frank Burns is far from satisfied. Hawkeye says if she observed anything, she would know that Burns does not know his way around and is an idiot. She says Burns is a good technical surgeon and a good military surgeon. She says the others should not address him as Hawkeye, and he says that is his name. She objects to the familiarity in a military organization. He says he is going back to drink Scotch and says he would have invited an attractive woman like her to go and share his bed; but he says she really put him off. He says they call someone like her a regular army clown.
O’Houlihan asks how a degenerate like that could have reached a high position in the medical corps, and Mulcahy says he was drafted.
Blake gets in a jeep and tells Radar he is going to see General Hammond and that Major Burns will be in charge while he is gone. Blake asks a nurse to have some buttons sewn on his shirts, and she says she will do it herself.
In the dining tent men are singing, and O’Houlihan complains to Burns about McIntyre’s vulgarity as he says he wants her clothes taken off.
O’Houlihan is typing a letter and reads it aloud to Burns who suggests it is for army morale. She reads it to him, and they both sign it. He says they make a good team, and she says they think the same way. He asks if she is hungry and says he is hungry for her and kisses her. After some kissing, she stands up and goes to mail the letter. She wishes she could deliver it personally. Burns offers to check on her personally.
The men and nurses are drinking beer.
Burns goes in to see O’Houlihan who says she is all right. He says they are godless buffoons. He objects to how they behave toward her. He is grateful to have her there, and she says the same. She says they have become close in a short time. He says God meant them to find each other. She says his will be done, and they start kissing and taking off their clothes. Radar puts a microphone under the tent.
Mulcahy comes in and listens to the radio show with the men, but they are hearing Burns and O’Houlihan. Mulcahy says he forgot something and goes out. McIntyre says he is such a sweet man. They hear her ask him to kiss her “hot lips,” and McIntyre says they have to share this with others.
Hawkeye and others hear it in surgery.
She tells Frank to wait because she can hear it. She tells him to get his pants. He asks her not to tell on him.
The next day men say it was an uplifting radio program. At breakfast O’Houlihan is jumpy, and she leaves the tent. Hawkeye sits with Burns and asks if he heard from his wife.
Blake returns and tells the captain he hoped she did not other with the shirts. She says they are done. Vollmer tells Blake there was nothing he could do about it. Blake sees Hawkeye talking to Burns and says that is encouraging.
Hawkeye says the guys asked him to find out from Burns what “Hot Lips” was like in the sack. He asks if it was better than self-abuse. McIntyre says that Hawkeye is trying to get Burns to sign up to make a personal tour of all the camps. Blake asks what he is saying, and Radar says that Hawkeye is asking Burns about a point of anatomy. Blake asks Radar what Burns is saying, and he says he is not saying much but must be formulating his answer. Hawkeye is asking what kind of sounds she made, and Burns tells him to shut his filthy mouth. Burns attacks him, and Hawkeye says Burns has gone nuts. McIntyre says that Burns is a sex maniac.
Burns in a strait-jacket is put in a military police jeep and taken away. Duke asks Blake if he punches Hawkeye, can he go home too.
Blood is spurting from a patient, and they move the patient. Hawkeye asks for two clamps. While he is working, an announcement says they have determined that marijuana is a dangerous drug.
Mulcahy asks to speak to Hawkeye outside and tells him that the dentist Waldowski has a problem. He learned about it in confession, and he can’t divulge it. Hawkeye asks if he can give a hint. Mulcahy says he can say how serious it is. He tells how during a poker game, he asks what does it matter because it is only a game. Hawkeye whistles and says he had better go see the man about a tooth.
Hawkeye goes to the tent where they are playing poker and says he has a toothache. He asks Waldowski for some of his Scotch. Waldowski is lying down and asks if a man is not a man, what does he have to live for. He says a nurse with big boobs was there last night, and he wasn’t going to fool around out here because he has three girls he is engaged to back home. Hawkeye says he is 7,000 miles from home. Waldowski says he took her out last night and failed. He says she wanted to, but he couldn’t do it. Hawkeye says that happens to everybody and to him four or five times. Waldowski says it never happened to him before. Hawkeye says he is the best equipped dentist there and a Don Juan, but Waldowski says that is a cover-up. He admits he is a fairy, a victim of latent homosexuality. Hawkeye asks if he has done anything, and Waldowski says it is only a matter of time. He says he can’t face it. He says if Hawkeye found out he was one, he would not like breaking the news to his wife. Hawkeye says he sees the problem, and Waldowski says he has it multiplied.
While roasting marshmallows McIntyre says that after racing they put Man o’ War out to stud. He had an average of about 130 foals a year, and he lived to be 36. When he died, they did an autopsy and found out he was a raving Queen. They talk about Waldowski, and Hawkeye says he is convinced that his obsession is a viable force. Waldowski comes in, and they try to act natural; but Hawkeye can’t help smiling. Waldowski says he knows they have been talking about him, and he came over to tell them that he is planning to commit suicide. One guy asks if he can have his record-player, and Waldowski says sure. Hawkeye says he will miss him and asks Painless how he plans to do it, and he suggests a 45. They say that is sloppy but reliable. Waldowski says that was what he wanted to ask them. McIntyre suggests a black capsule, and Waldowski asks what that is. They say it is simple and effective.
Mulcahy tells Hawkeye that he has to check with the vicar’s office because he cannot give absolution to a man who is going to commit suicide. Hawkeye says he is not going to do it; but he only intends to do it. He says if what they are doing works, then he will not kill himself. Therefore he will be preventing a mortal sin. Mulcahy says he has to check, and Hawkeye tells him to do so.
The doctors are sitting at a table for the last supper as taps is being played. Mulcahy looks in the window and sees Waldowski in the center. They say their farewells to Wald. Duke says he is going to the unknown to do some recon for them. They say he volunteered for this mission, and Hawkeye says that is what being a soldier is all about. McIntyre says that Dago Red has something to add. Mulcahy comes to Waldowski and prays over him. McIntyre gives him his black capsule, and Waldowski says it works fast and that he had better go lie down over there. Duke gives him a glass of wine to help him. Waldowski lies down in a coffin in front of the table as a man sings about how suicide is painless and brings on many changes, and he can take it or leave it as he pleases. He lies down on his back. They each walk by and give him something.
They carry the coffin outside in the dark. Hawkeye tells the pretty nurse he is glad she could come. They kiss, and he asks if she is leaving tomorrow. She says she is leaving in the morning. He says it will be rough on her husband. She asks why he is concerned with him. He says a man would be more considerate and would not go home a nervous wreck. She tells him he will have to stop using logic. She asks why he shouldn’t go to bed with her, and he says he did not mean him.
Waldowski is lying on a bed under a red lamp. Hawkeye brings the nurse in and says she has the rare privilege of bestowing life by a tender act of mercy. She sees him and asks if he is dead. Hawkeye says he has a problem, and she is the only person who can help him. She says no. He says she has to look on this as a service to Painless who really needs therapy while it will not do any harm to her. If she thinks her virtue is more important than his life, it is completely up to her. He asks her to stay there and look at him for a minute. He asks her to stay close to the whole man. He steps out, and she calls to him. She lifts up the sheet over him.
In the morning a nurse tells the pretty nurse she forgot her hat and tells her to have a good trip. The jeep leaves before a man can hand her traveling orders to her. Waldowski says it is a big day because he has two jaws to rebuild. He tells Hawkeye to have a good day and goes off to work. The pretty nurse lifts off in a helicopter and smiles.
They are working on a prisoner of war, and McIntyre says he needs help. They turn him and continue the surgery. He is tolerating it because he is young. They try to stop the spurting. Radar brings some blood from a donor.
Men in bathing suits are by a stream and a crashed helicopter, and they talk about the crash and then Hot Lips. Duke bets $20 she is not a real blonde. Hawkeye takes the bet. McIntyre says he will be a witness but asks how they are going to find out. Duke says they all have to see it together.
Hawkeye gets some wine, and McIntyre says it is past the time when the nurses usually take their showers. Hawkeye says they will be there. Four nurses and Hot Lips arrive in robes to take their showers. McIntyre asks Hot Lips if she would like to see the pictures of his kids, and she says she has no interest. She walks to the shower tent as Mulcahy comes out and changes the sign from “Men only” to “Ladies only.” McIntyre and Hawkeye bring chairs to sit and watch, and others gather with them. At a signal a rope is cut, and a weight falls that causes the tent wall to be lifted, revealing Hot Lips soaping in the shower. She screams and falls on the floor as they cheer and applaud the show. Other nurses go to help her. Duke says he won the twenty bucks. Hot Lips comes out in her robe and is very angry as she goes to see Col. Blake. She opens the door and sees that he is in bed with “Dish.” She says this is an insane asylum and that it is his fault because he does not do anything to discourage them. He asks her what she wants him to do. She tells him to put them under arrest. She says first they called her Hot Lips, and he let them get away with it. He let them get away with everything. She says if he does not turn them over to the MPs this minute, she is going to resign her commission. He tells her to resign. She leaves shouting about her commission. Blake asks Dish if she wants more wine, and she says please.
In a town Hawkeye is driving a jeep and saying something in Korean. Hawkeye takes young Ho-Jon (Kim Atwood) where the girls are and goes back to the jeep. A woman with a movie camera shouts to him and asks if he has been wounded yet. He says he has a slight wound. She asks if he wants to say hello to his mother, but he says she is dead. He says hello to his father instead. A Korean doctor brings Ho-Jon to Hawkeye and says he is examining him to see if he can be a soldier in their army. He says his heart-beat is much too fast, and his blood pressure is dangerously high. Hawkeye says he probably thinks he is not fit for service; but the doctor says he works in a military hospital, and he may have taken some drug. Hawkeye asks why he would do that. The doctor says he will keep him there for a couple days to find out the truth. He tells him to say goodbye to him and says it was a nice try. Hawkeye is frustrated.
McIntyre is hitting golf balls, and a helicopter lands. A soldier gets out and runs by Hawkeye and past sun-bathing nurses. The soldier comes back with another soldier who identifies McIntyre for him. The lieutenant came from Seoul to see him, and McIntyre says he does not look well and tells him to take his shirt off. Hawkeye sees it is an order to go to Japan, and the lieutenant explains that a Congressman said the only surgeon who can save his son is McIntyre. He says that Hammond wrote that he could take along someone to assist him, and he asks Hawkeye if he wants to come. He says yes. McIntyre says he can save him and gives him pills to take every half hour.
McIntyre and Hawkeye are driven in a jeep to a golf course in Japan. They go into a hospital and make a woman let them in. The head nurse finds them and says they can’t come in without permission. McIntyre gives her orders on arranging for the surgery he is going to do.
McIntyre and Hawkeye are operating, and Col. Merrill comes in. They tell him to get out and persuade him not to upset the Congressman. Marston (Michael Murphy) tells them about a whorehouse.
McIntyre and Hawkeye are pushed into the office of Col. Merrill and are told to wait there. They practice their putting on the rug. Merrill comes in and says they are under arrest. Hawkeye says they are staying one more day to check out the Congressman’s kid, and they are going to play golf. If he objects, they will tell their stories to the Congressman. Hawkeye tells him they will be in the pro shop.
Marston, McIntyre, and Hawkeye are eating in Japanese style with three Japanese women. A nurse talks to Marston, and he asks them to examine a child for him. He explains the case, and they say what they need.
While they are attending to this, Merrill comes in to arrest them again; but they give him gas.
Photos are taken of them with Japanese prostitutes.
McIntyre and Hawkeye come back in golf clothes and wear the shoes and socks during surgery. They go to the tent and tell Duke to open up. He delays, and they see him helping Hot Lips escape out the back.
Blake is working on his fishing again and gets a call from General Hammond (G. Wood) about a battle. He tells Blake he got accusations from O’Houlihan that are hard to believe. Blake tells him not to believe them and hangs up.
General Hammond arrives in a jeep and says he will be with Col. Blake. McIntyre and Hawkeye tell him that he can’t blame Blake because Hot Lips does not like her name. Hawkeye says she is a fanatic about ritual and won’t even let them play football. An officer tells Hammond she is lined up. He says he did not know they had a football team, and they say they do. Hammond says he coaches a team. He says they are deciding who they are to play, and they bet a few thousand on the games. He says they will find a date to play their team.
Hawkeye tells McIntyre and Duke that they can get Blake to ask for Dr. Oliver Harmon Jones who is better known as Spearchucker Jones who played with the 49ers.
Hammond tells Blake that if they had closer relations, they would not have this misunderstanding. He suggests a football game will help with a few bets. Hammond says it is one of the best gimmicks they have there. Blake asks about Major O’Houlihan, and Hammond says to screw her.
Duke says that Jones is the only Negro officer in the whole camp. Hawkeye says they will stick him in here with us. Duke is surprised that he is serious. Duke says it was enough for him to put with the two Yankees, but Hawkeye pushes him over.
Dr. Oliver “Spearchucker” Jones (Fred Williamson) has arrived and explains that he used to throw the javelin. Blake comes over to the group and says they are here to practice. He wants Jones to know that they are all on the same playing field. He says the three basic principles are organization, discipline, and teamwork. Jones suggests they limber up first.
The men are practicing and training as Blake barks orders. Blake and Jones agree that they look pretty lousy. Hawkeye says he has an idea how to bet their money. He says they can leave Jones out of the game in the first half. They bet half their money. In the second half they can get odds, put him in, and then clean up. They like the idea, and Blake suggests they have some plays. Jones says he drew up eight plays and shows them to him.
The nurses are cheerleaders, and the players are in red and blue uniforms. The opposing blue players are much bigger, and they return the opening kickoff for a touchdown. Jones says that number one played for the Rams and is called “Superbug.” Jones says they have to get him out of the ball game. Then they can stick to their strategy. Hammond tells his players to ease up a bit. The red team gets trapped for a safety. During the time-out a player puts a needle under his belt. They get a free kick, and Superbug returns it for a touchdown. He is tackled in the end zone, and someone gives him a shot. He collapses and is carried from the game. Hammond tells his team to kill them. They play rough. At half time the score is 16-0.
During halftime in the locker-room players remind Blake to place the bet. Blake goes to Hammond and asks if he wants to double the bet. Blake asks for odds, and Hammond gives them three to one on double the bet.
In the second half Jones runs for a touchdown. Hammond learns that Jones is a pro, and he accuses Blake of bringing in a ringer. Radar says their ringer identified our ringer. Players are getting injured and are collapsing from exhaustion. Hammond says his team is falling like dead flies. Jones runs well. A fight breaks out because their other black player says they called him a “coon.” Jones says that is a trick to get him thrown out of the game. He tells the player to use the name of that player’s girlfriend. That player gets angry and is ejected from the game. Blue players on the bench are smoking marijuana. The red team scores a touchdown on a pass play, making the score 16-12. Jones runs with the ball, and they call time-out. Jones tells them to use an unbalanced line, and he instructs the center to use a hidden-ball trick. The center hides the ball under his jersey and sneaks away and runs for a touchdown. The guns sounds, and they won 18-16.
They come back to camp in trucks.
During a poker game Hot Lips is sitting next to Duke.
Hawkeye is alerted and finds Duke in surgery. He says that Blake got their orders to go home. Duke asks when, and Hawkeye says whenever they want. The chief surgeon asks if he minds if they get out of this guy’s brains first. Hawkeye says he will see him and goes out.
Duke says goodbye to McIntyre and Jones. Mulcahy prays for the jeep they take. Hawkeye and Duke get in the jeep, and Hawkeye drives off. Blake asks if Hawkeye stole that jeep, and Radar says that is the one he came in. Blake says that is very good.
This comedy satirizes the futility of the Korean war that Americans fought so far from home. Instead of combat the story portrays the doctors who have to try to save the lives and patch up the wounded from the carnage. The times are reflected in the humor being based on sexual harassment, religious intolerance, and fear of homosexuality.