The song was written for Ken Prymus, the actor playing Private Seidman, to sing during the faux-suicide of Walter "Painless Pole" Waldowski (John Schuck) in the film's "Last Supper" scene. Director Robert Altman had two stipulations about the song for composer Johnny Mandel: it had to be called "Suicide Is Painless" and it had to be the "stupidest song ever written". Altman attempted to write the lyric himself, but, upon finding it too difficult for his "45-year-old brain" to write something "stupid" enough, he gave the task to his 15-year-old-son Michael, who reportedly 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. This more choral version was sung by uncredited session singers John Bahler, Tom Bahler, Ron Hicklin, and Ian Freebairn-Smith, and was released as a single attributed to "The Mash". Altman said that, while he only made $70,000 for directing the movie, his son had earned more than $1 million for co-writing the song.
Al De Lory recorded "Song from M*A*S*H", an instrumental jazz piano version for his 1970 album Al De Lory Plays Song from M*A*S*H. This version peaked at No. 7 on the adult contemporary chart during the summer of 1970.
Swedish group Small Town Singers released a version under the title "Song from M*A*S*H" in 1975. The single peaked at 17th position in Sweden, Top 100 chart in Australia.
^"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.'
^"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.