This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. The information presented in this report was obtained from studies on 21 patients who were admitted to the Osaka University Hospital in late August and early September 1945 suffering from an alarming malady designated atomic bomb disease by the Japanese. I observed, examined and followed approximately half of the patients, while information on the remaining patients was taken from the hospital records. The patients selected for presentation do not include those receiving severe blast injuries or extensive external burns at the time of the explosion. Included are patients who received minor or no injuries or burns during those catastrophic days at Hiroshima and Nagasaki but who subsequently developed severe clinical manifestations, which in 5 instances resulted in death. Seventeen of the patients herein presented experienced the atomic bombing at Hiroshima, Japan, on August 6, 1945, while the remaining 4 were victims of the Nagasaki explosion on Aug. 9, 1945. The