Captopril, a competitive antagonist of angiotensin converting enzyme, has been marketed in the United States for the treatment of resistant hypertension. Despite extensive study, its exact mechanism of action remains unclear; decreased renin‐angiotensin‐aldosterone and sympathoadrenal system activity as well as increased bradykinin and prostaglandin E and F activity have been postulated. The drug decreases peripheral vascular resistance. Controlled trials in resistant hypertension of various etiologies and chronic congestive heart failure have demonstrated sustained effectiveness and therapeutic benefits. Side effects include skin rash, loss of taste, proteinuria, and leukopenia; higher doses and concomitant renal dysfunction appear to be predisposing factors. The benefit‐to‐risk ratio for captopril clearly justifies its use in resistant cases of hypertension and congestive heart failure, but further experience is needed to evaluate its use in milder forms of these d