One-hundred-three patients with extensive non-small-cell lung cancer were entered into a prospective, randomized trial to determine the value of MER as an adjuvant to chemotherapy. Patients were stratified according to histology and performance status. All patients received CCNU, methotrexate, and Adriamycin with 48 patients also receiving MER. All patients had a performance status of 2 or less (less than 50% bedridden), 49% had prior radiation therapy, only one patient had prior chemotherapy, and all had extensive disease. Of the patients, 42% had epidermoid cancer, 21% had large cell cancer, 32% had adenocarcinoma, and 4% had mixed adenosquamous or undifferentiated carcinoma. The response rates and response durations of the two treatment regimens were similar. Of the patients, 18% had an objective response; in 4% it was complete. An additional 29% had a stable response. Median duration of response ranged from 21 to 23 weeks. Median survival rates for non-MER and MER treatment groups were 21.5 and 18.6 weeks, respectively. The four complete responders have a survival of 24, 85, 86+, and 129 weeks. MER did not improve response for hematopoietic tolerance, was associated with significant morbidity, and was poorly tolerated. The value of immunotherapy in lung cancer remains to be established.