The effect of concurrent chemotherapy and radiotherapy on breast cosmesis in the conservative treatment of breast cancer is controversial. The aim of this study was to investigate the effect on cosmesis of adding concurrent chemotherapy to conservative surgery and radiotherapy in the treatment of stage I or II carcinoma of the breast. Eligible patients were invited to complete a questionnaire examining physical changes contributing to cosmesis, patients' perceptions of these changes and the presence or absence of late side-effects. Responses were received from 145 women who did not receive chemotherapy and 39 who did. The mean overall cosmetic score (treated breast compared to untreated breast, measured on a scale of 1-10) was not significantly different between those who received concurrent chemotherapy and those who received radiotherapy alone (6.92 vs 6.95, P = 0.87). Breast appearance, perceptions of physical changes and treatment side-effects were similar in the two groups. We conclude that concurrent administration of chemotherapy (in this instance, intravenous CMF: cyclophosphamide, methotrexate and 5-fluorouracil) and radiotherapy in the treatment of early breast cancer has no detrimental effect on breast cosmesis as judged by patients.