Seventy-six patients with stage III bronchogenic carcinoma were treated with monthly adriamycin, cyclophosphamide, cis-dichlorodiammineplatinum(II), and vincristine. In addition, they were randomized to receive either no immunotherapy, the methanol extracted residue of bacillus Calmette-Guérin (MER), or Corynebacterium parvum (C. parvum). Age, histology, extent of disease, prior therapy, and performance status were comparable in the three treatment groups. Twelve patients (16%) died having received only one treatment cycle. Sixty-four of the 76 patients received two or more treatments and were evaluable for response. There were no patients with complete responses, 14 patients (18%) with partial responses, 28 patients (37%) with no change, and 22 patients (29%) with progressive disease. Survival among patients receiving C. parvum is significantly longer (P less than 0.05) than that of patients receiving either MER or no immunotherapy.