Introduction: Our objective was to determine the effects of intracoronal bleaching on the shear bond strength and failure side location of metallic brackets at 2 times (bleaching immediately before bonding and 30 days before bonding). Methods: Sixty freshly extracted mandibular incisors were randomly divided into 3 groups; each group contained 20 teeth. After finishing canal preparation and root canal filling, the root fillings were removed to a level 2mm apical to the cementoenamel junction. Glass ionomer base (Vitrabond, 3M Dental Products, St Paul, Minn) was placed approximately 2-mm thick. Bleaching agent (Whiteness Perfect, FGM Dental Products, Joinville, Brazil) was placed into the rest of the cavity for 4 days at 2 times. Shear bond strength of these brackets was measured in megapascals. The adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance (ANOVA), Tukey, and chi-square tests. Results: The bond strengths of the group with no bleaching (mean, 20.25 +/- 7.06 MPa) were significantly higher (P>0.001) than those of the group that had bleaching immediately before bonding (mean, 4.85 +/- 3.22 MPa) and the group that had bleaching 30 days before bonding (mean, 8.70 +/- 4.93 MPa). The results of the chi-square comparisons indicated significant differences among the 3 groups. In the group with no bleaching, there was a higher frequency of ARI scores of 2 to 4, indicating cohesive failures in the resin. In the other 2 groups, the failures were mostly adhesive at the resin-enamel interface (ARI scores of 4 and 5). Conclusions: Intracoronal bleaching with carbamide peroxide adversely affected the shear bond strength and changed the site of failure during debonding when bonding was done immediately or 30 days after bleaching. (Am J Orthod Dentofacial Orthop 2009;136:689-94)