This 3-part discussion of captopril, the first oral angiotensin converting enzyme (ACE) inhibitor, focuses on the clinical use and superiority of this agent to standard treatments and the new observations that use can improve the overall poor survival associated with heart failure. Today, as in the past, treatment of CHF includes digoxin and diuretics. Vasodilators have been relegated by some to the role of supplementing therapeutic regimens when patients remain symptomatic. Recently, controlled studies have shown that the introduction and supplementation of therapeutic regimens with ACE inhibitions and specifically captopril is associated with substantial clinical benefits: Symptoms are reduced as hemodynamics and exercise capacity improve, metabolic derangements (including fluid retention, potassium and magnesium loss and sympathetic nervous activation) are reduced with resultant favourable effects on arrhythmia frequency and finally the newest and most dramatic observation of improved survival. This review will briefly summarize these developments and assist in the clinically important aspects of this therapy for practicing physicians. Guidelines for the clinical use of captopril: In patients with confirmed dilated cardiomyopathy, captopril improves stroke volume in response to afterload reduction, but in volume-contracted patients vasodilation may be associated with hypotension. Therefore, prior to initiating captopril, the diuretic dosage should be reduced, particularly in low serum sodium concentration states if intravascular volume is depleted. Potassium supplements should be stopped due to the expected decrease of aldosterone production and improved potassium retention. Initial therapy should be started with a low captopril dosage (2 to 3 times 6.25 mg/day), maintenance dosages are 25 or 50 mg b.i.d. or t.i.d. Superiority to other vasodilator drugs and use in mild cases: In studies of acute and chronic CHF, captopril improves hemodynamics, exercise tolerance, and reduces symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)