[en] 239 Consecutive women with stage III carcinoma of the breast were treated by primary radiation therapy (RT) from 1977 to 1985. The response rate was 89%, the 5-year survival 40% and the local-regional tumor control (LTC) 59%. For the 27 non-responders, postirradiation chemotherapy was initiated but they died within 3 years. 105 Patients were subjected to mastectomy and axillary dissection after RT. In 107 cases, the RT was not followed by surgery. Systemic treatment consisted of hormonal therapy in both groups. The RT plus surgery group had better survival rate, 58% vs. 35% at 5 years. However, the incidence of less favorable cases was higher in the RT alone group. Histological findings in the operated group are analysed to determine prognostic significance of residual disease. No residual or only damaged microscopic disease was found in the breast in 36% of the cases. The axillary lymph nodes (ALN) were free of disease in 42% of the women. Patients with negative ALN after RT had significantly better 5-year survival (82% vs. 43%) and LTC (85% vs. 60%) rates. Decreased chest wall recurrence rate was associated with no residual or damaged microscopic disease in the breast (5% vs. 21%). The disease-free ALN were more common after 50-80 Gy telecobalt than after 40-50 Gy kV irradiation (51% vs. 33%). Primary tumor size (< 5 cm vs. > 5 cm) had no significant impact on histological findings or on prognosis. Residual disease is mainly a marker of tumor-host relationship which indicates the biological aggressiveness of the disease. 20 refs.; 4 figs.; 2 tabs