In many types of cardiovascular pathophysiology such as hypercholesterolemia and atherosclerosis, diabetes, cigarette smoking, or hypertension (with its sequelae stroke and heart failure) the expression of endothelial NO synthase (eNOS) is altered. Both up- and downregulation of eNOS have been observed, depending on the underlying disease. When eNOS is upregulated, the upregulation is often futile and goes along with a reduction in bioactive NO. This is due to an increased production of superoxide generated by NAD(P)H oxidase and by an uncoupled eNOS. A number of drugs with favorable effects on cardiovascular disease upregulate eNOS expression. The resulting increase in vascular NO production may contribute to their beneficial effects. These compounds include statins, angiotensin-converting enzyme inhibitors, AT1 receptor antagonists, calcium channel blockers, and some antioxidants. Other drugs such as glucocorticoids, whose administration is associated with cardiovascular side effects, downregulate eNOS expression. Stills others such as the immunosuppressants cyclosporine A and FK506/tacrolimus or erythropoietin have inconsistent effects on eNOS. Thus regulation of eNOS expression and activity contributes to the overall action of several classes of drugs, and the development of compounds that specifically upregulate this protective enzyme appears as a desirable target for drug development.