question: OBJECTIVES: The aim of this randomized double-blind controlled clinical trial was to evaluate different protocols for at-home use of 10% hydrogen peroxide in whitening effectiveness and tooth sensitivity. METHODS: Seventy-two patients were selected according to the inclusion and exclusion criteria, with the upper central incisors having color A2 or darker according to the Vita Classical scale (VITA Zahnfabrik, Bad Säckingen, Germany) and randomized into two groups: 10% hydrogen peroxide applied once daily for 15 minutes (HP 15) or applied once daily for 30 minutes (HP 30). Bleaching was performed for 14 days in both groups. The color was evaluated before bleaching, during bleaching (1st and 2nd weeks), and 1 month after the bleaching treatment using the Vita Classical, Vita Bleachedguide 3D-MASTER, and Vita Easyshade spectrophotometer (VITA Zahnfabrik). Dental sensitivity was recorded by the patients using the numerical rating scale (0-4) and visual analogue scale (0-10 cm). Color data were evaluated by two-way analysis of variance (ANOVA) of repeated measures (group vs. treatment time). The Mann-Whitney test was performed to contrast the means (&#945;=0.05). Tooth sensitivity was assessed by Fisher's exact test (p=1.00) and intensity of tooth sensitivity was evaluated by the Mann-Whitney test (&#945;=0.05) for both scales. RESULTS: A significant whitening effect was observed after 2 weeks of bleaching for all color measurements (p=0.01), with no difference between HP 15 and HP 30 (p>0.05). Also, the absolute risk and intensity of tooth sensitivity were similar (47%; p>0.05). CONCLUSIONS: The effectiveness and tooth sensitivity of at-home bleaching carried out with 10% hydrogen peroxide applied for 15 minutes or 30 minutes are similar.