The band has sold an estimated 11 million records in the U.S. while worldwide album sales are approximated at over 20 million.[citation needed] VH1 slotted the band at #79 on its "100 Greatest Artists of Hard Rock". Their 7th studio album, Infestation, was released April 20, 2010.

The origins of Ratt go at least as far back as 1976 with a San Diego band called Mickey Ratt, which was formed by founding member vocalist Stephen Pearcy. Several CDs have been released of the Mickey Ratt line-ups, including several demo compilations and a live concert.

Mickey Ratt went through various line-ups. Members included guitarists Jake E. Lee, Chris Hager, Paul DeNisco, and Bob DeLellis, bassists Matt Thorr, Tim Garcia, and Dave Jellison, Mike New, and drummers John Turner, Dave Alford, and Bob Eisenberg.

In 1980, the band moved to Los Angeles to increase their chances of landing a recording contract with a major label. The band recorded a single called "Dr. Rock" / "Drivin' on E", which was given to fans at their early Los Angeles club shows. Guitarist Jake E. Lee joined the Mickey Ratt line up.

In 1981, the band's name was shortened to Ratt. The band later worked at various fast food restaurants in order to pay back the studio time for their initial recording. Robbin Crosby played with the band later in the year. Jake E. Lee, Chris Hager, Matt Thorr, and Dave Alford all left Mickey Ratt to form another band called Rough Cutt. Guitarist Warren DeMartini joined in January 1982 (recommended by Lee). Bassist Gene Hunter (from Jake E. Lee's Teaser) and drummer Khurt Maier (who played drums on the early "Tell The World" recording) would temporarily play in Ratt before Bobby Blotzer and Juan Croucier (also with the band Dokken) . DeMartini was only 18 years old when he was called up to Los Angeles to join Ratt. At the time he was attending college in San Diego and reluctant to drop out to join a band that had, so far, had only limited success. Marq Torien briefly replaced DeMartini, though Warren returned in time for the recording of their EP, later in 1982 .

In July 1983 the band signed a recording contract with Time Coast Records and released an EP on the independent record label. With the self-titled Ratt EP, the band began to draw public attention from outside of Southern California. It contained the hit "You Think You're Tough". Also included was a cover of "Walkin' the Dog," originally a hit for Rufus Thomas in 1963. Ratt's version was a nod to Aerosmith, who had included a cover of the song on their influential first album in 1973. The track "Back for More" that appeared on the EP was a slightly different version of the one that appeared on their follow-up Out of the Cellar. The EP was a success (though it has been out of print for many years and is today considered a rare and valuable collectors' item). Bassist Joey Cristofanilli would step in for Juan Croucier, though Croucier would return after the band secured a deal with Atlantic Records. Cristofanilli would play bass on an alternate version of "You're In Trouble" that would appear as a bonus track on the Ratt EP (red-colored vinyl version) in Europe, and Cristofanilli also co-wrote "Wanted Man".

After a well-received, self-titled independent EP, the band signed with Atlantic Records and immediately started writing and recording what would be its first proper album Out of the Cellar. Released in March 1984, the breakthrough album was critically praised by both fans and critics alike at the time of its release. Milton Berle's guest appearance, dressed in his Uncle Miltie drag character, in the video for "Round and Round" helped draw even more attention to the band.

Out of the Cellar combined the then-prevalent Van Halen and Aerosmith influenced bravado elements with the then-novel muted, staccato guitar-picking style of Judas Priest.

The album scored much radio and MTV play with the blockbuster anthem "Round and Round" (which peaked at #12 on the Billboard Hot 100), "Wanted Man", "Back for More", and "Lack of Communication". Pearcy's raspy yet bluesy vocals melded well with the pyrotechnic guitar playing of twin leads Robbin Crosby and Warren DeMartini. Their music videos, especially for that of "Round and Round", exposed them to an impressionable teen audience first tuning into the then fledgling MTV cable network.

Out of the Cellar became a commercial success, going platinum many times over in the United States as well as making them stars in the Far East. The album catapulted the band to the top, capped off by an incredibly successful world tour that saw the band sell out countless stadiums and arenas worldwide. Out of the Cellar is today widely regarded as the band's best work and a definitive moment in 80s heavy metal.