Eleven patients with subcutaneous prosthetic breast implants were followed 3-16 years after mammary irradiation. Radiation doses ranged between 45 Gy and 50 Gy to the whole breast, supplemented in five cases with 10-21 Gy scar boost. Evaluation of the cosmetic results revealed a good score in three patients, moderate to fair in three, and poor in five. Of the five patients who had poor postirradiation cosmesis, three had fibrotic changes and encapsulation of the prostheses prior to the irradiation, and two received their irradiation 1 month after the reconstruction. In most of the patients, the nonirradiated breast was augmented with a prosthesis and both breasts could be followed for comparison. The irradiated side usually looked and felt on palpation worse than the nonirradiated, but both breasts exhibited a steady deterioration in appearance over time. The patients who enjoyed better cosmetic results after irradiation had better breast appearance before the radiotherapy. Of three patients treated with lower doses (45 Gy/4.5-5 weeks), two enjoyed good cosmesis. Both patients who received irradiation immediately after reconstructive surgery had poor cosmetic results. Three observations could be made: (a) when the implanted breast was free of fibrotic changes, radiotherapy produced acceptable results, (b) whenever feasible, 45 Gy/5 weeks seemed preferable over higher doses, (c) irradiation immediately after the reconstructive surgery appeared to produce poorer cosmetic results.