Objective: To compare whitening efficacy of Crest Professional WhiteStrips (6.5% H2O2), Day White (7.5% H2O2) and Nite White Excel (16% CP equivalent). Methods: Ninety subjects were randomly assigned to three groups (30/group). Maxillary impressions were obtained for fabricating custom jigs and trays. In addition to demographics and medical history, examinations of oral tissues,tooth shade of maxillary anterior teeth (Vitapan shade guide and chromameter) and tooth sensitivity (tactile, thermal and questionnaire) were conducted at the baseline, 3rd, 7th, 14th and 21st day (18th day for Day White). Subjects were asked to use the assigned products following instructions. Vitapan shade and chromameter data were analyzed using the ANOVA and Student-Newman-Keuls methods, and oral tissue and tooth sensitivity evaluations were descriptive. Results: The Vitapan shade and chromameter values, age, and gender distribution at the baseline were comparable among the three groups. The 3-day Vitapan shade changes were -2.93, -3.54 and -4.59 for the Crest, Day White and Nite White Excel, respectively; the shade reduction for Nite White Excel was significantly higher than those of the other groups. Nite White Excel had significantly greater Vitapan shade reduction than the other two groups throughout the study, and subjects who reached B1 at 7th, 14th and 21st were 11.1%, 44.4% and 53.8%, respectively. The chromameter scores and the DE* were similar to the Vitapan data, but the 3-day reductions was not significantly different among the groups. The detected sensitivity was minimal and comparable among the groups, while the self-reported sensitivity and gingival irritation were higher in Day White subjects. No clinical evidence of adverse effects on oral tissues was detected in any subjects. Conclusion: All three whitening systems evaluated are effective, with Nite White Excel being the most effective whitener as it provides significantly greater and quicker shade reduction. Supported by Discus Dental, Inc.