Purpose: The purpose of this study was to evaluate and compare the long-term performance of fixed partial prostheses supported by 2 or 3 implants. Materials and Methods: All patients treated with fixed partial prostheses supported by either 2 or 3 implants during the period 1985 to 1998 were included in this retrospective report. Annual clinical follow-up examinations were performed, with special attention to stability of the prostheses and peri-implant and occlusal conditions. Radiographic examination was performed when the prostheses were delivered (year 0) and subsequently at 1-year, 5-year, and 10-year examinations. Results: A total of 178 patients had received fixed partial prostheses (FPPs) during this period of whom 123 (77 women and 46 men) were available for follow-up (mean age = 65 years, range 32-91). These 123 patients received a total of 146 implant-supported FPPs (63 two-implant- and 83 three-implant-supported) supported by 375 implants. The mean observation periods for the 2- and 3-implant-supported restorations were 9.6 years and 9.4 years (range, 5 to 18 years), respectively. Survival rates for the 2- and 3-implant-supported prostheses were 96.8% and 97.6%, respectively. The implant survival rate after loading was 98.4% for both groups. The mean bone loss at the 5-year follow-up was 0.3 mm for the 2 groups. No significant differences in bone loss (P > .05), implant failure rate (P > .05), or incidence of mechanical complications (P > .05) were found between the 2 prosthesis designs. The complications differed, significantly, with more loose gold and abutment screws in the 2-implant-supported group (P .05) and more porcelain fractures in the 3-implant-supported group (P .05). Conclusion: The 2-implant-supported partial prostheses exhibited long-term clinical performance comparable to prostheses supported by 3 implants. (Comparative Cohort Study) Keywords: complications, dental implants, dental prostheses, partially edentulous, retrospective studies