The song was written specifically for Ken Prymus (the actor playing Private Seidman), who sang it during the faux suicide of Walter "Painless Pole" Waldowski (John Schuck) in the film's "Last Supper" scene. Robert Altman had two stipulations about the song for Mandel: first, it had to be called "Suicide Is Painless"; second, it had to be the "stupidest song ever written". Altman tried to write the lyrics himself, but found that it was too difficult for his 45-year-old brain to write "stupid enough". Instead he gave the task to his 14-year-old-son, Michael, who apparently wrote the lyrics in five minutes.
Altman later decided that the song worked so well, he would use it as the film's main theme, despite Mandel's initial objections. This version was sung by uncredited session singers John Bahler, Tom Bahler, Ron Hicklin and Ian Freebairn-Smith (the vocals are sometimes misattributed to Johnny Mandel, due to his being the only name officially credited for the song).
Grady Tate recorded a soul-jazz version of the song for his 1970 album After the Long Drive Home.
Al De Lory recorded a jazz piano version for his 1970 album Al De Lory Plays Song from M*A*S*H. This version peaked at #7 on the adult contemporary chart during the summer of 1970.
Henry Mancini recorded an easy listening version for his 1970 album Mancini Plays the Theme from Love Story.
Andre Kostelanetz recorded an easy listening version for his 1970 album Everything Is Beautiful.
Fung Bo Bo recorded a female-vocal version (in English) on a Malaysian EP (MMI Top 21006) in 1970.
Ahmad Jamal recorded an instrumental jazz-funk version for his 1974 album Jamalca. This version was included on some re-releases of the soundtrack album. Jamal recorded another version of the tune for his 1985 album Digital Works.
Roy Ayers recorded an instrumental version for his 1974 album Change Up the Groove.
Norrie Paramor recorded an instrumental version for his 1975 album Radio 2 Top Tunes Vol. 3.
Ray Conniff recorded an easy listening version for his 1976 album Theme from S.W.A.T. and Other TV Themes.
Bill Evans recorded a jazz piano trio version for You Must Believe in Spring, an album posthumously released in 1980, having made it a staple of his live sets for some years. Evans' version modulates through 4 keys. The song is also recorded in a jazz piano trio version on the CD Bill Evans Trio, recorded live in Buenos Aires in 1979.
Cal Tjader recorded a version for his 1981 album The Shining Sea.
Tripod did a short acoustic rendition of the theme in the song "Lingering Dad". Additionally, portions of the theme were later used in the song "Theme from Mash Guy" – a comedic song about a fictionalised writer of the song in an existentialist crisis over being known only as "the theme from M*A*S*H guy".
^"Interview with Johnny Mandel". JazzWax.com. October 24, 2008. Bob said to me, 'You know, I need a song for the film. It’s that Last Supper scene, after the guy says he’d going to do himself with a pill because his life is over, because couldn’t get it up with the WAC the night before.'
^Michael L. LaBlanc. "Gale Musician Profiles: Johnny Mandel". The Gale Group. The Theme for M*A*S*H (Suicide Is Painless) wasn’t intended to be the theme of the motion picture. It was written in 1970 for the "Last Supper" scene and was actually intended to be played by one of the actors. It had to be written before the movie was actually shot.
^"Interview with Johnny Mandel". JazzWax.com. October 24, 2008. Bob also said the song had to be called 'Suicide Is Painless'. 'Since [Capt.] Painless commits suicide with a pill, that would be a good title,' he said. Then he said, 'It’s got to be the stupidest song ever written.'
^"Interview with Johnny Mandel". JazzWax.com. October 24, 2008. Bob was going to take a shot at the lyrics. But he came back two days later and said, 'I’m sorry but there’s just too much stuff in this 45-year-old brain. I can’t write anything nearly as stupid as what we need.'
^"Interview with Johnny Mandel". JazzWax.com. October 24, 2008. Bob said, "All is not lost. I’ve got a 15-year-old kid who’s a total idiot." So Michael Altman, at age 15, wrote the lyrics, and then I wrote the music to them.
^Michael L. LaBlanc. "Gale Musician Profiles: Johnny Mandel". The Gale Group. His 14-year-old son, Mike Altman, was enlisted and wrote the lyrics in five minutes to which Mandel later added the melody.
^Michael L. LaBlanc. "Gale Musician Profiles: Johnny Mandel". The Gale Group. Later when the movie was being edited, Mandel heard the song being played over the film’s title in the helicopter scene and protested, saying, "It was the stupidest thing I have ever seen," and angrily walked out insisting it didn’t fit. The studio ignored his protest.