In 1951, the 4077th Mobile Army Surgical Hospital in South Korea is assigned two new surgeons, "Hawkeye" Pierce and "Duke" Forrest, who arrive in a stolen Army Jeep. They are insubordinate, womanizing, mischievous rule-breakers, but they soon prove to be excellent combat surgeons. Other characters already stationed at the camp include the bungling commanding officer Henry Blake, his hyper-competent chief clerk Radar O'Reilly, dentist Walter "Painless Pole" Waldowski, the pompous and incompetent surgeon Frank Burns, and the contemplative Chaplain Father Mulcahy.
The main characters in the camp divide into two factions. Irritated by Frank's religious fervor, Hawkeye and Duke get Blake to move him to another tent so newly arrived chest surgeon Trapper John McIntyre can move in. The three doctors (the "Swampmen", after the nickname for their tent) have little respect for military protocol, having been drafted into the Army, and are prone to pranks, womanizing, and heavy drinking. Frank is a straitlaced military officer who wants everything done efficiently and by the book, as is Margaret Houlihan, who has been assigned to the 4077th as head nurse. The two bond over their respect for regulations and begin a love affair. With help from Radar, the Swampmen sneak a microphone into a tent where the couple are engaging in sex and broadcast their encounter over the camp's PA system, embarrassing them badly and earning Houlihan the nickname "Hot Lips." The next morning, Hawkeye goads Frank into assaulting him, resulting in the latter's removal from the camp for psychiatric evaluation. Later, when Houlihan is showering, the Swampmen pull the tent sides off and exposing her naked body, in order to settle a bet over whether she is a natural blonde. Crying, furious and embarrassed, Houlihan screams at Blake for letting his staff run wild and failing to discipline them and threatens to resign her commission; Blake bluntly tells her she can resign her commission, which unsettles Houlihan enough to calm her down.
Painless, described as "the best-equipped dentist in the Army" and "the dental Don Juan of Detroit," becomes depressed over an incident of impotence and announces his intent to commit suicide, believing that he has turned homosexual. The Swampmen agree to help him carry out the deed, staging a feast to evoke Leonardo da Vinci's Last Supper, arranging for Father Mulcahy to give Painless absolution and communion, and providing him with a "black capsule" (actually a sleeping pill) to speed him on his way. Hawkeye persuades the gorgeous Lieutenant "Dish" Schneider—who has remained faithful to her husband and is being transferred back to the United States for discharge—to spend the night with Painless and allay his concern about his "latent homosexuality". The next morning, Painless is his usual cheerful self, and a smiling Dish leaves camp in a helicopter to start her journey home.
Hawkeye and Trapper are sent to Japan on temporary duty to operate on a Congressman's son and, hopefully, play some golf. When they later perform an unauthorized operation on a local infant, they face disciplinary action from the hospital commander for misusing Army resources. Trapper uses anesthetic gas to sedate the commander. Using staged photographs of him as he awakens in bed with a prostitute, they blackmail him into keeping his mouth shut.
Following their return to camp, Blake and General Hammond organize a football game between the 4077th and the 325th Evac Hospital and wager several thousand dollars on its outcome. At Hawkeye's suggestion, Blake applies to have a specific neurosurgeon – Dr. Oliver Harmon "Spearchucker" Jones, a former professional football player for the San Francisco 49ers – transferred to the 4077th as a ringer. Hawkeye also suggests that Blake bet half his money up front and keep Jones out of the first half of the game. The 325th scores repeatedly and easily, even after the 4077th drugs one of their star players to incapacitate him. Hammond confidently offers high odds, against which Blake bets the rest of his money. Jones enters the second half, which quickly devolves into a free-for-all, and the 4077th gets the 325th's second ringer thrown out of the game and wins with a final trick play.
Not long after the football game, Hawkeye and Duke get their discharge orders and begin their journey home – taking the same stolen Jeep in which they arrived.[6]
