Sleep was a memorable Californian stoner rock band from the 1990s. Their first album, Volume One, was released in 1991 on Tupelo Records, and is their most overlooked or ignored album. The vocals have a little more bite to them than on other releases, adding a tinge of hardcore to their music which was more often thought of as doom metal. In 1993 Sleep's Holy Mountain was released by Earache Records. It's a fan favourite, and is fondly imagined as what a long-lost Black Sabbath album from the early 70s might sound like, around the Master of Reality era.

There were technically two more Sleep albums but they are nearly identical, having been reworked and released under a different name and label. At the end of it all, 1999's Jerusalem became 2003's Dopesmoker: 63 minutes of weed-laced riffs and sing-chanting through endless bongloads. It's all one song, and although Dopesmoker is the preferred version, Jerusalem has its share of proponents who appreciate the rougher cut.

Sleep's music has been used in a couple films. Jim Jarmusch (a noted doom metal enthusiast if the all-Boris/Sunn O)))/Earth soundtrack to The Limits of Control is any indication) included a 10 minute long edit of Dopesmoker on the soundtrack of Broken Flowers, although it can only be heard in the film for about 10 seconds while it blares through the speakers of a car radio. The song Dragonaut plays for an extended period of time in the surreal Harmony Korine film Gummo while two central characters ride bikes down the main drag like they own it.

For most of its existence Sleep had only three members: Al Cisneros doing bass and vocals, Matt Pike handling guitar, and Chris Hakius on drums. Second guitarist Justin Marler was only around in the beginning, and left soon after Volume One. Chris Hakius would also leave, in 1997, and was replaced by Jason Roeder until the group disbanded in 2003. Matt Pike is currently involved with fronting the trio High On Fire, a faster, thrashier, and certainly more popular band than Sleep ever was. Al Cisneros and Chris Hakius went off and became known as OM, taking with them the mellow, soulful stoner vibe from Sleep, after High On Fire had plundered all of its violence and gravity.

Sleep reunited on stage at the 2009 All Tomorrow's Parties: The Fans Strike Back Festival, playing two special "never to be repeated" shows with the classic Cisneros-Hakius-Pike lineup. They later reformed for a second ATP festival in September 2010, this time in their home country, and embarked on a small tour.