"I Don't Know" is a 1952 recording by Willie Mabon and His Combo on Parrot Records (blues label) and Chess Records. The single was considered by many to be extremely influential on the development of U.S. R&B throughout and beyond the 1950's. Mabon's first and only chart hit, it reached number one on the U.S. R&B chart in December 1952.[1]. The lyrics were derived from a Cripple Clarence Lofton tune. In 1978, The Blues Brothers covered the song and released it on their number-one live album, Briefcase Full of Blues.