An updated version of "25 or 6 to 4" was recorded for the 1986 album Chicago 18 with James Pankow listed as co-writer. With the new band member Jason Scheff on lead vocals, the single reached number 48 on the U.S. chart. This version was also used as the B-side for the band's next single in 1986, "Will You Still Love Me?".
The song is about trying to write a song in the middle of the night. The title refers to the time of day in which the song is set: 25 or 26 minutes before 4 AM. The song's writer, Robert Lamm, was trying to write a song at that time one night, in a room above the Whisky a Go Go, deciding to write a song about his own struggle to do so. (He had recently written and sung "Does Anybody Really Know What Time It Is?", another Chicago hit.) Because of the unique phrasing of the song's title, "25 or 6 to 4" has been incorrectly speculated to be a veiled reference to drug quantities, or a mystical allusion.