Objective: Quantitative Light-induced Fluorescence (QLF™) measures the change in autofluorescence of tooth caused by demineralization; however stain on tooth surface exhibit the same phenomenon so QLF may possibly measure the change in stain intensity by bleaching products. This study determined the use of QLF to compare stain-removal by whitening toothpastes and a bleaching gel. Methods: 220 extracted human teeth were randomly assigned to six experimental groups: 10% carbamide peroxide bleaching gel (CPgel) (A, n=10), whitening toothpastes applied with (B) and without (C) brushing (5 brands, n=10/brand), conventional toothpastes applied with (D) and without (E) brushing (5 brands, n=10/brand), and distilled water (F, n=10). Teeth were stained by cycling between human saliva and tobacco solution. Following staining, QLF image of each tooth was taken before and after 3 bleaching episodes, and the images were analyzed for quantification of the stain intensity (DQ). Group A was given 8-hour treatment (simulating manufacturer's bleaching instruction); while other groups were either brushed (B, D, F) or not brushed (C, E) for two minutes, on each treatment episode. Results: Comparing the mean DQ before and after 3 bleaching episodes in each group using paired t-test (α=0.05), each group exhibited a statistically significant (p<0.01) reduction in stain, with the greatest reduction showed by CPgel (53.6%). The stain-removal efficacies of all groups with brushing were comparable B(42.2%), D(41.8%) and F(34%). Similarly, the stain removing ability of two groups without brushing but same products as brushed groups were comparable C(28.2%) and E(21.5%), indicating brushing as the key stain removing factor and not product constituents. Conclusion: QLF measured the stain-removing ability of different products. The study suggests the stain-removal property of whitening toothpastes to be dependent mainly on mechanical brushing, and inferior to that of CPgel. "Supported in parts by NIDCR, Grant #DE14318 for COSTAR Program and Ultradent Products Inc."