To examine the effects of a 10 percent carbamide peroxide bleaching gel on the oral soft tissues, the authors conducted a prospective, double-blind, placebo-controlled clinical investigation. Fifty-two patients completed a two-week treatment regimen, applying either a placebo or a 10 percent carbamide peroxide gel in a soft tray for eight hours a day. Clinicians examined the participants' oral soft tissues at baseline and one week, two weeks and six weeks after the first treatment. The examiners recorded the Silness and Loe plaque and gingival indexes, nonmarginal gingival index and nongingival oral mucosal index at each examination. The data collected at these intervals did not indicate that any soft tissue damage had occurred as a result of the bleaching regimen.