"25 or 6 to 4" is a song written by Robert Lamm for the rock band Chicago. To this day, it is one of the most frequently played Chicago songs on classic rock and album-oriented rock stations. It was recorded for their second album Chicago (1970) with Peter Cetera on lead vocals. The song was edited and released as a single in June of that year, climbing to number 4 on the U.S. Billboard Hot 100 chart and number seven on the UK Singles Chart. This recording features an electric guitar solo using a wah-wah pedal by Chicago guitarist Terry Kath .