Forty-nine patients with chest wall recurrences of breast carcinoma received radiation therapy and 915-MHz microwave hyperthermia for 95 lesions. Follow-up ranged from 3 to 39 months, with five patients dying before 6 months follow-up. At 1 month follow-up, 49 (52%) of 95 lesions showed complete response; 28 (29%), partial response; and 18 (19%), no change. At 6 or more months follow-up, 54 (67%) of 81 lesions demonstrated local control; 10 (12%), partial response; six (7%), no change; and 11 (14%), local-regional recurrences. Superficial blisters occurred in 24 (25%) of 95 lesions, whereas long-term complications (deep necrosis, subcutaneous burns) occurred in seven (7%) lesions. Relapse occurred in 16 (17%) lesions, seven after initial complete response and nine after partial response. Several prognostic treatment factors were identified: applied radiation dose (greater than 30 Gy, P less than .01), size of tumor (less than 6 cm diameter, P less than .001), minimum tumor temperature (greater than 41 degrees C, P less than .001), and status of disease (M0 or M1 vs M2, P less than .001). Treatment complications were correlated with maximum temperatures (greater than 45 degrees C, P less than .001). In summary the palliative treatment concept proved to be safe and effective.