There are now extensive data suggesting that the progression of atherosclerosis can be altered by cholesterol-lowering therapy. The changes in stenosis severity, measured angiographically, are small relative to the clinical benefit noted. Other factors, in addition to changes in stenosis severity, are probably operative. Effects of cholesterol-lowering on endothelial function, perhaps mediated by reductions in PAI-1 levels, may be one of these mechanisms. This uncontrolled study requires further investigation to elucidate the independent relation between lovastatin, PAI-1, and fibrinogen. © 1994.