The chemotherapy dose intensity for breast cancer has been recently considered to be an important factor in determining clinical outcome. Many trials have shown routine postoperative irradiation to have a detrimental effect on the delivered dose of adjuvant chemotherapy. In this paper the impact of radiotherapy on the dose intensity of adjuvant chemo- or hormonotherapy was evaluated in 237 breast cancer patients. 177 patients had radical mastectomy and 60 quadrantectomy followed by radiotherapy. Chemotherapy comprised 6 cycles of FEC (5-fluorouracil, epidoxorubicin, cyclophosphamide) alternated to 6 cycles of CMF (cyclophosphamide, methotrexate, 5-fluorouracil)+tamoxifen for 5 years. There were no significant differences in the adjuvant chemotherapy dose intensity in the mastectomy group compared to the radiotherapy group.