Angiotensin converting enzyme inhibitors (ACE-I) are widely used in patients with severe heart failure on the basis of the significant improvement in mortality in the CONSENSUS-I trial in patients with Class IV heart failure. Recent data from the 5-year clinical trial Studies of Left Ventricular Dysfunction (SOLVD) suggest a role for ACE-I in patients with mild to moderate heart failure as well as in those with asymptomatic left ventricular dysfunction. The SOLVD treatment trial in patients with a left ventricular ejection fraction (LVEF) less than or equal to 35% and treated for heart failure with conventional therapy including digitalis, diuretics, or vasodilators demonstrated that the addition of enalapril resulted in a significant reduction in mortality from heart failure as well as in the combined end point of death plus hospitalization from heart failure. These data suggest that ACE-I should be the base of therapy for patients with mild to moderate heart failure, as well as for those with severe heart failure.