This study evaluates the effect of a previous cancer on the clinical characteristics and the outcome of lung cancer patients. The 313 primary lung cancer patients operated on in the Osaka University Hospital during the period 1984-1993 were reviewed. Of those, 37 had a history of previous cancer. In the lung cancer patients with a history of previous cancer, 20 had adenocarcinomas, 14 had squamous cell carcinomas, while 3 had other cancers. The previous malignancies included 13 gastric cancers, 10 head and neck cancers, 6 colorectal cancers, and 8 others. The pathological stage was 17 stage I, 1 stage II, 15 stage IIIA, 1 stage IIIB, and 3 stage IV. The 5-year survival rate was 37.9%. In patients without a history of previous cancer, there were 139 adenocarcinomas, 100 squamous cell carcinomas, and 37 others. The pathological stage was 126 stage I, 33 stage II, 74 stage IIIA, 23 stage IIIB, and 20 stage IV. The 5-year survival rate was 43.3%. There were no significant differences in the cell type, stage, or survival between the lung cancers found as the first and second cancers. Lung cancer patients with a history of previous cancer are expected to respond to a resection as well as those with lung cancer appearing as their first cancer.