Seventy-three patients with small cell lung carcinoma refractory to standard chemotherapy were entered in this phase II randomized study of cisplatin, maytansine, and chlorozotocin. Of the 58 evaluable patients, only one partial response was observed among 21 patients given cisplatin, and no responses were seen among 19 given maytansine or 18 given chlorozotocin. One patient treated with chlorozotocin and two treated with cisplatin experienced life-threatening thrombocytopenia. One third of the maytansine-treated patients experienced moderate or severe neurologic toxicity. The overall median survival was 9.7 weeks. Chlorozotocin treatment was associated with inferior survival (7.7 weeks).