39/Smooth is the debut studio album by the American punk rock band Green Day. It was released on April 13, 1990 through Lookout Records on vinyl (black and green) and cassette. It is the band's only studio album to feature John Kiffmeyer on drums.
Jesse Michaels of Operation Ivy contributed the artwork on the album. The inner sleeve shows handwritten lyrics by Billie Joe Armstrong and letters by drummer John Kiffmeyer and Lookout owner Larry Livermore to I.R.S. Records, rejecting an offer to sign to the label and declaring their loyalty to Lookout! Records (however, the band would later leave Lookout! and move to a major label, Reprise Records).
39/Smooth was later featured in its entirety, along with the group's two previous extended plays Slappy, 1,000 Hours and the song "I Want to Be Alone" (from The Big One, a compilation album released by Flipside Records in 1990) on the compilation album 1,039/Smoothed Out Slappy Hours in 1991.