Objectives: It has been suggested that tooth whitening might cause considerable pain. The aim of this study was to evaluate subjective intensities of pain during bleaching of vital teeth and to assess the patients' contentment with the treatment outcome. Method and Materials: Thirty patients were treated for 1 week in a double-blind study design. Employing gels containing 17%, 10%, or 0% (control group) carbamide peroxide, patients wore bleaching trays for 2 hours per day and described subjective intensities of pain while wearing the trays by means of a visual analog scale. The patients' subjective contentment with the bleaching outcome was measured with an intermodal intensity comparison. Results: For the 17% gel, a median value of 3.5 U (max: 10; min: 1) for pain intensity was observed; this was statistically different from the value seen with the 10% group (2.0 U; max: 7; min: 0) (P .05). Both test groups differed significantly from the control group, which had a median value of 0.0 U (max: 3; min: 0) (P .05). Patients' contentment with the treatment outcome did not differ between the test groups (P > .05), although statistical differences were observed between the control and the test groups (P .05) after bleaching for 1 week. Conclusion: Application of carbamide peroxide-containing bleaching agents to vital teeth causes pain correlated with the agent's concentration. Since both highly and less concentrated gels might result in a similar contentment with the treatment outcome, the use of highly concentrated agents appears not to be justified to improve vital tooth color. Keywords: carbamide peroxide, concentration of bleaching materials, contentment, customized bleaching tray, pain, patient satisfaction, vital tooth bleaching