Eleven patients with laryngeal cancer associated with additional primary tumors underwent cutaneous delayed hypersensitivity tests and lymphocyte stimulation studies with phytohemagglutinin for evaluation of their cellular immunity. Five of the 11 patients were anergic or hypoergic as shown by skin tests to recall antigens and seven of nine patients had impaired lymphocyte transformation. Depressed immunity was more often observed in patients with an active malignancy. The level of serum immunoglobulins was elevated in two of eight studied patients, and in the remaining patients was within the normal range. All patients had a history of excessive smoking. Most frequently, second tumors were found in the lung, urinary tract and skin. The prognosis seemed to be determined by the additional tumor rather than by the laryngeal cancer.