A recently reported technique for bleaching vital discolored teeth involves the use of a mouthguard and 10% carbamide peroxide without preoperative etching or postoperative polishing of the enamel. This in vitro study evaluated the effects of the bleaching agent on the surface texture of the enamel. Thirty-three extracted teeth were subjected to 10% carbamide peroxide for a period equivalent to 5 weeks of nighttime wear. A control area on each tooth had been covered and sealed. All discolored teeth experienced lightening, but there was no difference in color between the treated and control areas; the color-changing effects apparently extend to portions of the tooth not in direct con tact with the solution. Epoxy replicas of the teeth were examined under a scanning electron microscope. No etching was apparent, and no difference in surface texture between treated and control areas was detected.