MASH juxtaposes gory operating-room procedures with anti-establishment humor. Occasionally, these two elements coexist within the same shot. For example, while Hawkeye is amputating a patient's leg, he asks a nurse to scratch his nose, when all the while the sound of the saw cutting the bone is audible.

The film, the plot of which is episodic, is marked by Altman's trademark editing style, in which many scenes contain several simultaneous or overlapping conversations, as well as his frequent use of zoom.

Some really sharp surgeons

In the Autumn of 1951, the 4077th Mobile Army Surgical Hospital is in need of replacements, and is assigned two: Captain "Hawkeye" Pierce (Donald Sutherland) and Captain "Duke" Forrest (Tom Skerritt). On their arrival, it becomes clear that they are rebellious, womanizing, mischievous rule-breakers (they arrive having "borrowed" a Jeep, and immediately begin flirting with the nursing staff), but they soon prove beyond argument that they are also good at their jobs. They immediately clash with their new tent mate Major Frank Burns (Robert Duvall), who is both a religious man and an inferior surgeon. Hawkeye and Duke put pressure on Lt. Colonel Henry Blake (Roger Bowen), the unit's CO, to have Burns removed from "their" tent. At the same time, they ask him to apply to have a specialist thoracic surgeon assigned to the 4077th.

The new chest-cutter

The mysterious new thoracic surgeon arrives, and gives away little about who he is or where he's from. Hawkeye, though, is convinced he has seen the new man somewhere before. It is only after an impromptu football game that Hawkeye recalls a college football game he played in which he scored the only touchdown by intercepting a pass from the opposing team's (Dartmouth) quarterback, the new thoracic surgeon, Captain "Trapper" John McIntyre (Elliott Gould).

The new chief nurse

Major Margaret Houlihan