Cardiotonic pill (CP) is a pharmaceutical preparation of the herbal medicine Salvia miltiorrhiza. In vitro studies demonstrate that CP inhibits vascular endothelial expression of adhesion molecules and smooth-muscle proliferation, implying the possibility of antiatherosclerotic effects. This study employs an in vivo animal model to examine the potential therapeutic efficacy of CP on atherosclerotic development. Male apolipoprotein E-deficient (ApoE-/-) mice fed with an atherogenic (high fat) diet were administered with CP (90-120 mg/kg per day) via drinking water for 8 weeks. Hypercholesterolemia developed in the mice, with 22-fold increases in plasma levels of total cholesterol, 29-fold of LDL, and 7-fold of HDL. CP therapy did not significantly alter the lipid levels. Expression of intercellular adhesion molecule 1 significantly increased in circulating leukocytes and was abolished by CP therapy. Atherosclerosis significantly developed in the aorta and was attenuated by CP therapy, with an approximately 30% reduction in whole atherosclerotic lesions and an approximately 50% reduction in fibrous plaques in the artery. Thus, herbal medicine CP partly protects ApoE-/- mice from high-fat diet-induced atherogenesis. The protection is unlikely to be attributable to decreases in circulating cholesterol levels, but it might possibly relate to an inhibition of expression of adhesion molecules and other effects that remain unknown at this time.