Objective: The aim of this study was to evaluate the clinical efficacy of home-administered vital bleaching procedures and possible adverse effects derived from their use. One gel containing 3.5% hydrogen peroxide with a 5% potassium nitrate component (FKD, Kin Lab) was compared with a carbamide peroxide-based gel with a concentration of 10% (Opalescence, Ultradent). Method and Materials: Two sample groups were designed, each composed of 8 patients. All patients employed both bleaching products, 1 in the maxillary arch and the other in the mandibular arch on a random basis. The treatment was applied for 3 hours a day for 4 weeks. The degree of bleaching was evaluated using the Vita guide arranged by brightness. Dental sensitivity was measured with a specially designed 4-point scale. Gingival irritation was registered by the presence or absence of lesions in the marginal gingiva related to treatment. Results: The degree of bleaching was similar with both products (4.8 Vita shade tabs). The hydrogen peroxide product with potassium nitrate provoked less dental sensitivity, although the difference between the 2 products was insignificant (P = .063). Gingival irritation appeared in 6 subjects, but was unrelated to the applied product. Conclusion: Under the conditions of this study, no statistically significant differences were detected between 3.5% hydrogen peroxide containing 5% potassium nitrate (FKD) and the 10% carbamide peroxide-based product (Opalescence). Keywords: carbamide peroxide, home bleaching, hydrogen peroxide, potassium nitrate