Fifty-eight extracted incisors were artificially stained to compare the efficacy of sodium perborate preparations used for intracoronal bleaching. All teeth were bleached for a 6-day period and the bleaching pastes replaced at days 1 and 3 (walking bleach technique). Sodium perborate-monohydrate, trihydrate, or tetrahydrate in conjunction with 30% H2O2 as well as tetrahydrate, either mixed with H2O or prepared as an experimental gel, were placed intracoronally at a level of 1-mm below the vestibular cementoenamel junction. Standardized slides were used to evaluate the color changes during bleaching. Success rates between 46 and 77% could be achieved, but no significant differences in final bleaching results between any of the sodium perborate types were observed. The use of the experimental gel resulted in comparable esthetic results (54%), although the portion of tetrahydrate in the gel was lower than that of the other preparations. In contrast to general recommendations that bleaching agents be left for 3 to 7 days in the access cavity before replacement, shorter bleaching intervals did not seem to affect the success.