Carcinoma of the lung is the number one cancer killer in the United States. The overall cure rate is about 10%, and although resection is the best treatment available, five-year survival following operation is only 25%. Recent studies have shown that patients with lung cancer are immunosuppressed but that pulmonary tumors do contain tumor-associated antigens. Studies of other human tumors indicate that immunotherapy can augment tumor immunity and can be an effective surgical adjuvant. This communication reviews the basic principles of tumor immunology, with emphasis on the immunology of lung cancer, and discusses how these principles may be applied to the therapy of lung cancer.