Adjuvant chemotherapy (CT) is increasingly being used in conjunction with radiation therapy (RT) in the treatment of early stage breast cancer. To assess the effect of CT on the cosmetic outcome of the irradiated breast, we retrospectively reviewed the cosmetic results of patients who received either cyclophosphamide-methotrexate-fluorouracil (CMF) or doxorubicin-based chemotherapy in conjunction with breast irradiation between 1968 and 1985. The overall cosmetic results were evaluated by the physician as "excellent," "good," "fair," or "poor" using a standardized scale. The CT group consisted of 170 patients treated with CT and RT administered either concurrently or sequentially (CT before RT, after RT, or both) with a minimum of 24 months of cosmetic follow-up. These were compared to an RT alone control group of 170 patients who did not receive CT and were matched by tumor size, radiation technique, and year of treatment. At 36 months, the cosmetic scores for the CT group compared to RT alone were 47% versus 71% excellent (p less than 0.01), 36% versus 19% good, and 17% versus 9% fair or poor. For the 50 patients treated with concurrent CMF and RT, the scores were 31% excellent, 45% good, and 24% fair/poor, whereas for the 118 patients treated with sequential RT and CT they were 54%, 31%, and 14%, respectively. There was no difference between those patients who received sequential CMF and those treated with doxorubicin. We conclude that adjuvant chemotherapy adversely affects the cosmetic outcome of breast irradiation, but that this effect is not clinically significant unless CMF is administered concurrently with RT. Patients treated with either sequential CMF or doxorubicin-based CT had only a slight decrement in their cosmetic result compared to patients treated without CT.