We initiated a prospective randomized multicenter trial to clarify the role of radiotherapy in the treatment of the primary tumor in small cell lung cancer stage limited disease. Patients were randomized to receive only chemotherapy (n = 27), or chemotherapy and radiotherapy of 30 Gy (n = 34) or chemotherapy and radiotherapy of 50 Gy (n = 30). Radiotherapy was administered after the third chemotherapy cycle. All patients received prophylactic totalbrain irradiation of 30 Gy. The chemotherapy consisted of 6 cycles of adriamycin, cyclophosphamide and vincristin (ACO). 415 patients entered the trial. According to eligibility criteria 97 patients were randomized and 91 patients were eval·uable for response. The total response rate (CR and PR) was 69% not being statistically different between all groups. No differences in survival time were observed between patients receiving 30 Gy (median = 13.5 months) and those receiving 50 Gy (median = 12.4 months). However patients treated with radiotherapy and chemotherapy showed a statistically significant improvement of survival time compared to patients receiving chemotherapy alone (median = 9.7 months)