The aim of this study was to assess the color alteration and sensitivity of teeth throughout and following in-office bleaching. Twenty-two volunteers participated in this clinical trial of bleaching treatment (35% hydrogen peroxide bleaching gel and placebo) applied on maxillary incisors and canines. According to a splitmouth design, the volunteers' maxillary hemi-arches received either the bleaching or placebo agent, applied four times, at 1-week intervals. Color alteration and tooth sensitivity were assessed throughout and following bleaching. Statistical calculations were performed using gamma distribution and repeated-measures ANOVA. There was a statistically significant difference between teeth submitted to a bleaching agent and placebo (P .001). At the end of the first, second, third, and fourth sessions, the bleached teeth presented color scores statistically lower than those observed immediately before bleaching. There was no difference in the color scale scores of the bleached teeth between bleaching sessions. The sensitivity data test showed a significant difference among treatments (P .0001). Color alteration and dental sensitivity were altered by the bleaching agent.