The long-term cosmetic outcome of breast implant reconstruction is unknown. The morbidity and cosmetic outcome of 360 patients who underwent immediate postmastectomy breast reconstruction with various types of implants have been analyzed prospectively over a 9-year period. Of these patients, 334 who completed their reconstruction were suitable for evaluation of their cosmetic outcome. The early complication rate (< 2 months) was 9.2 percent, with an explantation rate of 1.7 percent. The late complication rate (> 2 months) was 23 percent, with a pathological capsular contracture rate of 11 percent at 2 years and 15 percent at 5 years and an implant removal rate of 7 percent. The revisional surgery rate was 30.2 percent. The cosmetic results were assessed prospectively using an objective five-point global scale. Every patient was scored at each visit once surgery was completed. The overall cosmetic outcome deteriorated in a linear fashion, from an initial acceptable result of 86 percent 2 years after patients completed their reconstruction to only 54 percent at 5 years. This decline in cosmetic outcome was not associated with the type of implant used, the volume of the implant, the age of the patient, or the type of mastectomy incision employed. Radiotherapy was not a significant factor because only 28 patients were irradiated. Upon Cox model analysis, pathological capsular contracture was the only factor that contributed significantly to a poor cosmetic outcome in which p < 0.0001 (relative risk 6.3). Despite a high revisional surgery rate, deterioration still occurred, suggesting that other unaccounted for variables were responsible. On photographic retrospective review of the patients without capsular contracture who demonstrated deterioration in their cosmetic scores, it became clear that a possible reason for their poor results was late asymmetry produced by the failure of both breasts to undergo symmetrical ptosis with aging.