Purpose:The aim of this prospective study was to report long-term treatment outcomes (prosthetic and implant related) of edentulous patients treated with implantsupported fixed prostheses who participated in the first clinical implant study in North America. Materials and Methods:Forty-five patients were treated with Brånemark implants supporting a total of 47 fixed prostheses (42 mandibular and 5 maxillary) between 1979 and 1984. All patients were recalled regularly for comprehensive prospective clinical and radiographic assessments. Results:Thirty-one patients (33 prostheses) attended a final recall visit in 2002; 71% of patients had been followed for 20 years (range 18 to 23 years), with overall prosthetic plan and implant outcome success rates of 84% and 87%, respectively. Mean marginal bone loss around the implants after the first year of loading was small (0.05 mm/year), with high individual variations. Poor oral hygiene, smoking history, and implant position appeared to be predictors of marginal bone loss. Prosthetic maintenance was ongoing and included fractured components and replacement of prostheses; the longevity of a fixed prosthesis for this group of patients was 8.39 ± 5.30 years. Conclusion:This study confirmed the overall long-term treatment outcome success of patients treated with fixed prostheses supported by Brånemark implants. Successful osseointegration with small mean bone loss was maintained as study patients aged, although prosthetic maintenance was required. The latter consideration should be discussed with all patients seeking such treatment. Int J Prosthodont 2004;17:417–424.