Patients with locally recurrent and metastatic breast carcinoma require effective palliation of pain and complicating cutaneous, soft tissue, and lymph node metastases. Since October 1989, 48 consecutive patients with recurrent breast carcinoma after mastectomy and no further surgical option were entered in a phase I-II study comparing two radiochemotherapy (RCT) regimens. Treatment-related toxicity was analyzed in 48 patients together with short- and long-term efficacy in 44 patients who had a minimum follow-up of at least 1 year. Since October 1989, group A (28 patients) received 60 Gy "split-course" radiotherapy (RT) over 10 weeks with two breaks of 2 weeks each after the second and fourth week of RT. Simultaneous 5-fluorouracil, methotrexate, and cyclophosphamide (CMF) was given during RT. From October 1991 to April 1993, group B (20 patients) received 54-60 Gy "conventional" RT over 6 weeks. Simultaneous 5-fluorouracil/mitomycin C was applied in the first and fifth week. Overall response [complete response (CR) + partial response (PR)] was 82% in group A (CR, 21%). Five of 28 patients developed grade 3-4 toxicity (EORTC/RTOG/WHO). Overall response rate in group B was 87% (CR, 19%). In this group, 6 of 20 patients experienced grade 3-4 toxicities. In both groups, the rate of local response was remarkably lower in patients with distant metastases and a short relapse interval < 2 years. Although both regimens achieved a similar local response rate, group B patients experienced a higher toxicity rate than did group A patients, but the treatment duration was considerably shorter. The local tumor response was greatly influenced by the extent of systemic disease.