Thirty-four previously untreated patients with oat cell carcinoma of the lung were treated with a myelotoxic combination of cyclophosphamide, adriamycin, methotrexate, CCNU, and Corynebacterium parvum (regimen A) every 4 weeks, interspersed with a non-myelotoxic combination including bleomycin, vincristine, dehydroemetine, and Corynebacterium parvum (regimen B) weekly the other 3 weeks or when hematologic toxicity prohibited administration of regimen A. Hematologic toxicity was frequent but was never a serious problem except in two cases of profound leukopenia in which fatal supervening infection occurred. Nineteen patients in this series (56%) showed a complete response lasting from 4+ to 65+ months. Eight of these patients are still alive with a followup of 6+ to 65+ months. Nine patients (26%) showed a partial response (greater than 50%) lasting 1-10+ months. Only one patient in this group is surviving (10+ months). The overall response rate was thus 82%. It is concluded from this study that only a complete response has any significant effect on survival, the benefit of a partial response over no response being only slight. The results achieved are compared to those of available series in the literature and from this comparison strategic deductions for the treatment of oat cell carcinoma of the lung are made.