In the story, the title refers to the telephone number that one dials to schedule an assisted suicide with the Federal Bureau of Termination. Vonnegut's 1965 novel God Bless You, Mr. Rosewater describes a story by the name and attributes it to his recurring character Kilgore Trout, but the plot summary given is closer in nature to the eponymous tale from Vonnegut's short-story collection Welcome to the Monkey House.
The setting is a society in which aging has been cured, individuals have indefinite lifespans, and population control is used to limit the population of the United States to forty million, which is maintained through a combination of infanticide and government-assisted suicide. In short, for someone to be born, someone must first volunteer to die. As a result, births are few and far between, and deaths occur primarily by accident.
Head over to the MacLane Library to read the full story!