This study clinically evaluated the alteration of color, color stability, dental sensitivity and gingival irritation on patients undergoing dental bleaching using varying bleaching methods and light-activation sources. According to pre-established criteria, 40 patients were selected and randomly divided into four groups (n=10): Group 1--35% Hydrogen Peroxide (HP); Group 2--35% HP plus Halogen Curing Light XL 3000 (3M/ESPE); Group 3--35% HP plus Demetron LED (Kerr) and Group 4--35% HP plus LED/LASER (Bio-art). For all groups, there were two sessions of bleaching with 35% HP, with a one week break between sessions. At each bleaching session, three applications of the bleaching gel were used. Two methods of shade evaluation were performed before and after the first week, second week, first month and after six months of the bleaching treatment. These methods were VITA Easyshade Spectrophotometer and Vita Classical Shade Guide. Statistical analysis using ANOVA demonstrated equality between the participating groups when evaluating the group and time variables. The In-Office dental bleaching treatments of vital teeth with 35% HP did not prove to be more effective when light sources were used. There was no difference in color stability between groups until the sixth month of evaluation.