Seventy-nine patients with metastatic or unresectable bronchogenic carcinoma were treated with a regimen of combination chemotherapy which included methotrexate, Oncovin (vincristine), cyclophosphamide, and adriamycin (MOCA), and were randomized to receive no additional therapy, immunotherapy with bacillus Calmette-Guérin, or immunotherapy with Corynebacterium parvum (C. parvum). The response rate and estimated median survival time were 68% and 42 weeks in small cell carcinoma and 18% and 29 weeks in other histologic types. Improved survival correlated with high performance status and response to therapy. Immunotherapy did not improve response, time to progression, or hematopoietic tolerance of chemotherapy. C. parvum was associated with significant morbidity and was poorly tolerated. MOCA appears to be of modest value in the treatment of bronchogenic carcinoma, particularly of the small cell type. A role for immunotherapy remains unproven.