Objectives: To evaluate the morphologic, mechanical, and chemical effects of carbamide peroxide bleaching agents on human enamel in situ. Method and Materials: Enamel slabs from extracted human teeth were divided in two and mounted on contralateral sides of removable maxillary appliances fabricated for three participants. Soft vinyl trays were adapted intraorally over the arch; one side contained a bleaching agent, and the other served as a control. Vital bleaching was conducted in vivo three times with three different bleaching agents and with new enamel specimens each time. Tests of Knoop microhardness, scanning electronic microscopy (SEM), and energy dispersive x-ray (EDX) were performed and analyzed by ANOVA. Results: No statistically significant differences were found between matched test and control specimens concerning microhardness values, morphology, or elemental content. Conclusions: Enamel surface showed no mechanical, morphologic, or chemical changes following bleaching in situ with three different carbamide peroxide agents. Keywords: EDX, microhardness, vital bleaching