In a population of 142 patients with stage I and II breast cancer, treated with tumor excision and external radiotherapy, using a wide range of radiation doses and fractionation schedules, an attempt was made to quantify the cosmetic outcome. Quantitative measurements of nipple displacement and breast contour retraction were compared and correlated with qualitative scoring by a panel. In the vast majority, the quantitative assessments correlate very well with subjective, qualitative scoring, making this method relevant for clinical use. There are a few exceptions, mainly cases where localized skin changes such as severe telangiectasia or skin necrosis affect strongly the cosmetic result but can go undetected in this measuring system. Also limited surgical deformations, which can detract seriously from cosmetic success, particularly when they occur in the medio inferior quadrants, can not always be assessed by this method. The routine use of these measurements in clinical practice is very simple. Only one photograph, taken in standard conditions is needed. Measurements can be carried out quickly, using the plotting device of a treatment planning system. This system may be of great use for follow-up of new treatment modalities and the study of the development of radiation fibrosis in breast cancer.