The antibacterial activity of three commercial 10% carbamide peroxide bleaching agents (Nite White, Karisma, and Opalescence) on Streptococcus mutans, Streptococcus mitis, Streptococcus sanguis, Lactobacillus casei, and Lactobacillus acidophilus was examined. Chlorhexidine (0.2%) was used as a positive control. Test materials and control solution were inserted in wells punched on the surface of disk sensitivity agars seeded with bacteria. After incubation of 24 to 48 h, zones of inhibition were measured. All three of the test materials displayed greater inhibition than the control. The pH of the solutions did not effect the bacterial inhibition.