Although the onset mechanism of arteriosclerosis remains unclarified at present, it seems that arteriosclerosis and cholesterol in blood are closely associated. This point has been indicated by the results obtained in many animal and human experiments. A high incidence of arteriosclerosis in dise-ses with high values of cholesterol in blood such as diabetes, nephrotic syndrome, essential hypercholesterol of blood seems to support this view. Therefore, drugs that correct the abnormality of fat metabolism are generally used for the treatment of arteriosclerosis. The authors have administered such drugs as MER-29 (Triparanol), unsaturated fatty acid (Athero), and chondroitin sulfate (Chondoron) as cholesterol inhibitors to the patients and obtained the following results. 1. Effects of cholesterol inhibitors Triparanol was quite effective on hypertension, arteriosclerosis and diabetes but not much effective on nephrosis. Athero was effective on 40-50% of the cases of hypertension, diabetes and nephrosis. Chondoron was found to be effective in less than one half of the cases of hypertension and arteriosclerosis, but showed hardly any effect on diabetes. Only it gave relatively better results than Triparanol and Athero. 2. Side-effects of these drugs In the administration of Triparanol there occurred not a single case of cataract and by taking a proper care of the dose it was possible also to prevent other side-effects to a considerable extent. Athero showed hardly any side-effect and on this point it is an excellent agent.