In February 1938 there were 2 patients in the Lancaster General Hospital at the same time, both of whom showed large interatrial septal defects at necropsy. The purpose of this paper is to present the 2 cases and to review the literature since 1934, at which time Roesler made an extensive clinical study and a complete review of the literature on this subject. He collected 62 cases, including a case of his own. REPORT OF CASES Case 1. —A 76 year old white man, a locomotive engineer, was admitted to the hospital on Feb. 17, 1938, complaining of headache, poor vision and a heavy feeling over the front of the chest. He had had a sore throat many times as a child, scarlet fever, "lung fever" (at age of 10 years) and pneumonia (in 1935). At the age of 18 years he had a "bad heart" and was in bed