Materials and Methods: Fifty patients will be selected for this single-blind, parallel, randomized-controlled clinical trial. The whitening treatment with 37% carbamide peroxide or 35% hydrogen peroxide (control) will be carried out in a single application of 45 minutes for two sessions with a 7-day interval. The sensitivity level will be assessed before, during and 24 hours after the procedure using verbal and analogic visual analogue (VAS) scales. Color alteration will be assessed by a bleach guide scale 7 days after each session and 30 days after the last session. Relative risk to sensitivity will be calculated and adjusted by session; while comparison of overall risk will performed by McNemar's test. Data on the sensitivity level for both scales will be subjected to the Mann-Whitney tests (α = 0.05). The color change will be measured with a spectrophotometer using the CIE L * a * b * and the L*, a * and b * parameter delta data, and ΔE and Δ00, will be individually subjected to two-way repeated measures ANOVA test to compare the two bleaching techniques at each evaluation time (α = 0.05).