Since 1981, 40 patients with advanced breast carcinoma have been treated with megavoltage radiotherapy combined with hyperthermia. The irradiation dose to the primary tumour was 50 Gy/25 fractions, five fractions per week. Hyperthermia (aim: 44 degrees C/30 min) was applied once a week, 30 minutes after the midweek radiation fraction. Tumour response did not correlate with the chance of long-term local control. The likelihood of 3-year local control was 46 per cent and 3-year survival was 52 per cent. The local tumour control rate decreased with increasing T stage and was related to non-uniformity of the temperature distribution in the heated volume. It was concluded that (a) the radiation dose should be increased and (b) the temperature uniformity should be improved.