The long cosmetic outcome of breast implant reconstruction is unknown. The morbidity and cosmetic outcome of 360 patients who underwent immediate breast reconstruction with various types of implant has been prospectively analysed over a 10-year period. 334 patients who completed their reconstruction were suitable for evaluation of their cosmetic outcome. The early complication rate (<2 months) was 9.1%, with an explantation rate of 1.6%. The late complication rate (>2 months) was 23%, with a pathological capsular contracture rate of 11% at two years and 15% at five years, and an implant removal rate of 7%. The revisional surgery rate was 30.2%. The cosmetic results were prospectively assessed using an objective five point global scale. Every patient was scored at each visit once surgery was completed. The overall cosmetic outcome deteriorates in a linear fashion from an initial acceptable result in 86% of patients two years after completion of their reconstruction to only 54% at five years. This fall off in the 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 as only 28 patients were irradiated. However, on Cox model analysis pathological capsular contracture was the only factor which significantly contributed to a poor cosmetic outcome(P<0.0001 (relative risk 6.3). In spite of a high revisional surgery rate, deterioration still occurred, suggesting that other unaccounted for variables were responsible. On photographic retrospective review of those patients without a capsular contracture who demonstrated a deterioration in their cosmetic scores, it became clear that a possible reason for their poor result was late asymmetry produced by the failure of both breasts to undergo symmetrical ptosis as the patients aged.