Tissue selectivity of pravastatin sodium (pravastatin) in inhibition of cholesterol synthesis was investigated and its effect was compared with other 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, such as lovastatin, simvastatin and ML-236B. Inhibition of cholesterol synthesis in vivo was measured by incorporation of radioactivity into the sterol fraction 1 h after intraperitoneal injection of [14C]acetate to mice. The drugs were orally administered to mice 2 h before the acetate injection. When pravastatin at a dose of 20 mg/kg was administered to mice, about 90% inhibition of cholesterol synthesis was observed in liver and ileum, but the inhibition was less than 14% in kidney, spleen, adrenal, testis, prostate and brain. This tissue selectivity of pravastatin was also demonstrated even in varying doses (5-100 mg/kg) and time (75-180 min) after drug administration. Other 3-hydroxyl-3-methylglutaryl coenzyme A reductase inhibitors did not show such a tissue-selective inhibition of sterol synthesis under the same conditions. These results obtained with the in vivo study were confirmed in vitro by the inhibition of sterol synthesis in various cultured cells and rats lenses, as well as by cellular uptake of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.