The results of non-specific immunotherapy adjuvant to surgery in the treatment of non-small cell lung cancer were studied in three separate randomised clinical trials involving 344 patients. The first study involved 126 patients. In 73, intrapleural BCG was given according to McKneally's technique. They were compared to a control group of 63 patients. In the second trial, levamisole was administered to 43 patients who, in addition to surgery, also had radiotherapy. These were compared with 43 control patients. In the third study, 60 patients underwent surgical operation for limited lesions and in addition received Isoprinosine. These were compared with a control group of 60 patients. All patients in the control groups of the three studies had similar surgical operations to their treated counterpart. The overall results showed no difference between those who received immunotherapy and the control groups of patients and that the use of these agents did not alter either the course of the disease or the incidence of its recurrence.