CS-514 (Eptastatin, Sankyo Co., Tokyo) inhibits 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and in studies in man this drug has proved to be free of major side effects and to be hypocholesterolemic (Kazumi, Yoshino, Kasama, Iwatani, Iwai, Morita and Baba 1986). CS-514 lowers LDL-cholesterol without decreasing HDL-cholesterol and does not affect glucose metabolism (Yoshino, Kazumi, Uenoyama, Inui, Kasama, Iwatani, Iwai, Yokono, Otsuki and Baba 1986). In this study we examined the effect of this drug on plasma triglyceride levels of hypercholesterolemic subjects and determined whether the drug modifies a lipoprotein structural model proposed by Morrisett, Jackson and Gotto (1977).