A randomized controlled study of adjuvant immunotherapy was performed using Nocardia rubra cell wall skeleton (N-CWS) for inoperable lung cancer patients in 5 institutions from October, 1978 to June, 1981. All patients without pleural effusions were treated according to common protocol including chemotherapy and/or radiotherapy, and the patients on performance status 0 to 3 were randomized to control and N-CWS group. In N-CWS group, 400 micrograms N-CWS was injected once or twice into the bronchial tumor using fiberoptic bronchoscope, and sequentially 200 micrograms N-CWS was injected once a month into the skin from shoulder to upper arms. One year survival rate of 118 N-CWS-treated patients was excellent when compared to that of 108 control patients, but statistically not significant. According to histological type, survival period of the patients with small cell carcinoma was prolonged significantly in N-CWS group. The eligible patients with pleural effusions were initially randomized to control group and N-CWS group and treated under tube thoracostomy. In control group adriamycin was injected into the affected pleural cavity. In N-CWS group adriamycin and N-CWS were injected with the same method, and intracutaneous injections of 200 micrograms N-CWS were added once every month. Not only response rate for pleural effusions but also survival rate were statistically excellent in N-CWS group. Main adverse reactions of N-CWS were skin lesions in the injected sites and fever, but these were transient and not serious.