Between 1970 and April 1982, 592 women with T(1), small T2, N0, N1, M0 breast cancer were managed by lumpectomy, axillary dissection and radiotherapy at the Institut Gustave-Roussy (IGR). The overall cosmetic result and the degree of asymmetry, fibrosis and telangiectasia of the treated breast were assessed by the radiation oncologist at each follow-up visit. The changes in these cosmetic parameters with time are shown. At 5 years the overall cosmetic result was excellent in 59%, good in 38% and fair or poor in 8%. A multivariate analysis was performed of the factors associated with a cosmetic defect. The most significant factors were tumour size, the presence of defect after surgery and the daily applied dose per fraction to the breast. Surgical and radiotherapy technique (especially alternate day fractionation) can significantly affect the cosmetic result obtained.