On counting the Heinz's Bodies in the circulating blood in healthy and various diseases, with considerations especially for abnormally increased cases, the following results were obtained. 1. A slight increase of Heinz's Bodies in the erythrocytes of healthy individuals was noted by such manipulations as lavation with saline and centrifugal precipitation. 2. Increased Heinz's Bodies were observed in the cases of severe acute hepatitis, subacute yellow liver atrophy and of severe acute nephritis. It was postulated that the increase resulted from toxic effects of the diseases and from depressed splenic functions. 3. Administrations of various sulfonamides cause increased Heinz's Bodies. 4. A marked increase of Heinz's Bodies was noted in the livercirrhosis case with gigantic splenomegalia. This was thought that the increase was due to losing diposition to Heinz's Bodies. 5. Also increased Heinz's Bodies were noted in the cases of acute intoxication of sleeping drugs, Grave's disease, angina pectoris and of myocardial damages. The mechanism of the increased Heinz's Bodies was not clear, but probably due to the drugs administered for their treatments. 6. There were increased Heinz's Bodies in the cases of essential hypochromic anemia, hypoplastic anemia and of thrombocytopenic purpura, probably due to regeneration of immature erythrocytes.