Vocalist Beth Gibbons and keyboardist Geoff Barrow first met in a job-retraining program offered by the unemployment office in Bristol, England. Gibbons, who came from Devon, was a veteran of numerous local bands, and Barrow, who hailed from nearby Portishead, had already accumulated studio experience as a teenager, working on vocalist Neneh Cherry's Homebrew, producing a track for fellow Bristol artist Tricky, and remixing tracks for Primal Scream, Paul Weller, and Depeche Mode. Along with guitarist Adrian Utley and sound engineer Dave McDonald, Barrow and Gibbons began collaborating on new music, using odd and elaborate recording techniques, sampling bits of spy-movie soundtracks, and employing a Theremin, the electronic instrument responsible for the eerie whine in vintage sci-fi movies and the Beach Boys' "Good Vibrations." The band's first effort was a short film, To Kill a Dead Man, which Barrow and Gibbons wrote and performed in. The project and its unusual soundtrack won record-label attention. The group signed to the U.K. label Go! Discs, which released 1994's Dummy, whose unanticipated success in England popularized the style dubbed "trip-hop," an atmospheric, nearly narcotic sound, mixing hip-hop beats with the downtempo undertow of dub reggae, oddly skewed samples, and the studio experimentation of electronic music, and was first realized by the Bristol group Massive Attack. Portishead added a fixation with James Bondish movie soundtracks, a jazzier flow, and Gibbons' sexily mournful vocals. Released on London Records in the U.S. the next year, the album became an underground sensation, reaching #79 and selling more than 150,000 copies after a video for the single "Sour Times (Nobody Loves Me)" (#53, 1995) garnered frequent airing on MTV.

It took two more years for the group to release its followup, Portishead (#21, 1997), which found Barrow striving to move beyond the sound that had become widely emulated, even on TV commercials. Portishead's next release was an album of remixes, Glory Times, followed by the live album, PNYC (#155, 1998), recorded at New York's Roseland Ballroom.