M*A*S*H aired weekly on CBS, with most episodes being a half-hour in length. The series is usually categorized as a situation comedy, though it has also been described as a "dark comedy" or a "dramedy" because of the often dramatic subject matter.

The show is an ensemble piece revolving around key personnel in a United States Army Mobile Army Surgical Hospital (MASH) in the Korean War (1950–53). The "4077th MASH" was one of several surgical units in Korea. The asterisks in the name are not part of military nomenclature and were creatively introduced in the novel and used in only the posters for the movie version, not the actual movie.

Early seasons aired on network prime time while the Vietnam War was still ongoing; the show was forced to walk the fine line of commenting on that war while at the same time not seeming to protest against it. The show's discourse, under the cover of comedy, often questioned, mocked, and grappled with America's role in the Cold War.

Episodes were both plot- and character-driven, with several narrated by one of the show's characters as the contents of a letter home. The show's tone could move from silly to sobering from one episode to the next, with dramatic tension often occurring between the unwilling civilian draftees of 4077th – Hawkeye, Trapper John, and B.J. Hunnicutt, for example – and the "regular Army" characters, such as Margaret Houlihan and Colonel Potter, who enlisted voluntarily. Other characters, such as Lt. Col. Blake, Maj. Winchester, and Cpl. Klinger, help demonstrate various American civilian attitudes toward Army life, while guest characters played by such actors as Eldon Quick, Herb Voland, Mary Wickes, and Tim O'Connor also help further the show's discussion of America's place as Cold War participant and peace maker.