A cooperative clinical trial by 25 Veterans Administration Hospitals to study the possible benefits of administering cytoxan in conjunction with surgical resection for bronchogenic carcinoma is reported. A total of 1008 patients in whom the diagnosis was established only at the time of operation by frozen section and who had surgical excision of the tumor were randomized into the study. Those patients randomized into the treatment group received 6 mg/kg body weight of cytoxan administered into the pleural cavity at the close of operation and the same dosage intravenously on postoperative days 1, 2, 3, and 4. A second course of drug was given in the fifth postoperative week and consisted of 8 mg/kg body weight of cytoxan given intravenously on five successive days. Reported complications and evidence of toxicity, although slightly higher in the treated group of patients, resulted in no significant increase in mortality at either the 30‐day or 90‐day postoperative period. Long‐term survival studies showed no improvement in patients receiving the drug. Even in those patients who received the two full courses of drug as prescribed by the protocol no treatment benefit was apparent. Extensive analysis of the data to detect any possible factors such as cell type or lymph node involvement which may have been influenced by the administration of drug remains to be done. The use of cytoxan in conjunction with surgical excision for lung cancer produces no improvement in long‐term survival when employed in the dosage regimen employed in this study.