CURRENT vital statistics emphasize the medical importance of any means of gaining information about lung cancer. Through its unique ability to delineate major intrathoracic vascular structures, angiocardiography constitutes a useful addition to the diagnostic methods employed in the study of carcinoma of the lung in the living patient.1The chief function of all clinical and laboratory procedures, including angiocardiography, is to demonstrate the nature and extent of pathological change within the patient. The accumulation of such information is a prerequisite to evaluation from a diagnostic, prognostic, and therapeutic viewpoint. The survey reported here indicated that angiocardiographically demonstrable vascular change occurs in 87% of cases of lung cancer. In 43% of the cases studied there is vascular evidence indicating probable inoperability of the lesion. METHOD AND RESULTS Case material for the present report consisted of 100 consecutive microscopically proved instances of carcinoma of the lung studied by angiocardiography. The first