Purpose: No clinical evidence has been provided to suggest that metal-free all–composite resin indirect restorations are a functional and esthetic alternative to all-ceramic restorations. The aim of this study was to evaluate the clinical performance of single-tooth computer-aided design/computer-assisted manufacturing (CAD/CAM)–generated all–composite resin and all-ceramic crowns after 3 years of function. Materials and Methods: In a prospective trial, 200 all–composite resin and all-ceramic crowns were rated over a 3-year period. Restorations were evaluated at 3 weeks and 1 and 3 years after insertion by the California Dental Association quality evaluation index, the patient’s self-assessment, marginal fit, periodontal parameters, volume loss, and wear patterns of the veneering material. Statistical analysis was performed using t tests (a = .05). Results: Cumulative survival and success rates after 3 years were 87.9% and 55.6% for all–composite resin and 97.2% and 81.2% for all-ceramic crowns, respectively (P < .05 for success rates). Restoration loosening occurred exclusively for all–composite resin crowns cemented on a cast post. All-ceramic restorations demonstrated satisfactory esthetic results. All–composite resin crowns resulted in significantly more mean total volume loss and mean vertical wear at occlusal contact areas after 6 months and 3 years of function. The clinical performance of the CAD/CAM-generated all-ceramic crowns used in this study was similar to that of other all-ceramic CAD/CAM systems. Conclusion: For up to 3 years of function, all–composite resin single-tooth restorations have inferior success rates compared to all-ceramic restorations. Due to the inferior esthetics and wear resistance of all–composite resin crowns, all-ceramic crowns remain the preferred treatment for CAD/CAM-generated metal-free single-tooth restorations. Int J Prosthodont 2010;23:223–230.