One hundred fifty-three patients with limited and 167 with extensive small cell carcinoma of the lung (SCCL) were evaluable for response to treatment with six courses of chemotherapy (cyclophosphamide, doxorubicin, and vincristine), irradiation to intrathoracic disease, and prophylactic cranial irradiation (PCI). No maintenance chemotherapy was given. Fifty-two percent of patients with limited disease (LD) and 10% of extensive disease patients (ED) achieved a complete response. The median survival times for LD and ED patients were 49 and 34 weeks, respectively. These results were compared to a previous experience with 147 patients who were treated with three courses of similar induction chemotherapy and thoracic irradiation, as well as one year of maintenance chemotherapy (CCNU, procarbazine, and methotrexate) but without PCI. Although the use of PCI was found to reduce the frequency of brain metastases as the site of first relapse, detailed comparisons of response rates and survival showed no significant differences between the two study populations. Prolonged maintenance chemotherapy of the type used in the first study does not favorably influence outcome after intensive induction therapy for SCCL.