Most patients with locally advanced non small cell lung carcinoma are treated with external thoracic radiotherapy. Because of the high incidence of distant metastasis the addition of chemotherapy has been proposed. The present randomized study was conducted from June 1983 to February 1989 and included 353 patients. The trial compared arm A, thoracic megavoltage radiotherapy alone at a total dose of 65 Gy in 26 fractions and 45 days, to arm B that comprised the same radiotherapy preceded and followed by 3 monthly cycles of VCPC (vindesine 1.5 mg/m2 d 1-2, cyclophosphamide 200 mg/m2 d 2-4, cisplatinum 100 mg/m2 d 2 and lomustine 75 mg/m2 d 3). Disease was deemed unresectable but non-metastatic after bronchoscopic, radiologic, CAT, and nuclear scans and physical examinations. Only patients in clinical, radiological, endoscopic, and histological complete remission were considered as locally controlled; these patients were monitored by fiberoptic bronchoscopy and systematic biopsies to the primary site. One hundred seventy-seven patients received thoracic radiotherapy alone and 176 received the combined modality. Twenty-seven percent of arm B patients had an objective response after 2 VCPC cycles. At the time of final assessment, performed 3 months after the end of thoracic radiotherapy in both arms, there were 20% of complete responders in arm A versus 16% in arm B. The two-year survival rate was 14% in arm A versus 21% in arm B (p = 0.08, logrank test). The distant metastasis rate was 67% in arm A versus 45% in arm B (p less than 0.001). Local control at 1 year was poor in both groups (17% and 15%, respectively). The striking effect of VCPC chemotherapy on the incidence of distant metastasis did not have a significant impact on overall survival. We conclude that thoracic tumor control remains a significant problem in unresectable non small cell lung cancer.