Pravastatin, a novel inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, was administered to nine hypercholesterolemic patients with diabetes mellitus to examine its effects on diabetic nephropathy. Pravastatin treatment resulted in lowering serum total cholesterol by 22.1% on the average (p less than 0.001), and led to a significant reduction in urinary excretion of albumin and beta 2-microglobulin in patients with an elevated urinary protein excretion rate at the baseline period. But glycemic control, blood pressure, urinary excretion of creatinine and that of N-acetyl-beta-D-glucosaminidase showed no significant change during the study. These results suggest that reduction of atherogenic lipids and lipoproteins with pravastatin could alleviate diabetic glomerular injury.