The Southwest Oncology Group entered 453 patients with extensive small cell carcinoma into a combined modality treatment program, involving a randomized comparison of three different chemotherapy regimens for remission induction, and of maintenance chemotherapy alone versus maintenance treatment with cycles of reinduction added at six and 12 months. In addition, there was systematic comparison of diagnosis by institutional pathologist versus review panel pathologist. No difference was observed among the three different induction arms with respect to the incidence of response to treatment (61%), complete response (16%), or survival duration (median, 31 weeks). Neither overall response rate nor survival are superior to previous results. However, patients who achieved a complete response demonstrated significant survival benefit if they were in the group who received reinduction chemotherapy, as opposed to maintenance alone. This observation may apply most importantly to patients with small cell lung cancer of limited extent, for whom complete response is achieved in a majority. Agreement of institutional and review panel pathologists on the diagnosis of small cell lung cancer was observed in 94% of reviewed cases. A final observation is that the omission of chest irradiation results in a dramatic increase in the incidence of initial relapse at the primary tumor site. This suggests that future studies will need to use better therapy for local control in responding patients.