Endothelial dysfunction appears to be an early event in most forms of cardiovascular disease. The dysfunction may involve a decreased formation, inactivation, or action of nitric oxide or prostacyclin as well as an increased formation of contracting factors,eg, prostaglandin H2and endothelin-1. Cardiovascular drugs can improve endothelial function either indirectly through their effects on cardiovascular risk factors, such as hypertension, hyperlipidemia, and diabetes or directly through endothelial actions. Direct and indirect endothelial protective effects of cardiovascular drugs may significantly contribute to normal organ perfusion and a reduced incidence of myocardial infarction, stroke, and renal failure in patients. Endothelium-dependent vascular regulation in health and in various cardiovascular diseases as well as the effects of currently available cardiovascular drugs are reviewed.