Five-year follow-up data of 100 patients with Stage III breast cancer treated by primary irradiation from 1977 to 1981 are presented. The 5-year overall survival rate for the entire group was 38 per cent with a median survival time of 33 months. The data were analysed to determine factors associated with prognosis. Patients with shorter premedical history and premenopausal status had a modest survival advantage. Response to radiation therapy, primary tumor status, regional lymph node condition, postirradiation histologic findings in axillary lymph nodes proved to have a prognostic value. Disease which was not controlled by radiotherapy also tended to be resistant to chemotherapy and the 5-year survival in this group was zero. Risk factors have to be taken into consideration for the combined modality treatment for stage III breast cancer. However, further studies are needed to define the indication and appropriate sequence of systemic treatment in this stage of the disease.