The high prevalence and poor prognosis of heart failure are a major concern. Hospitalization for heart failure accounts for a major proportion of health-care expenditure. A number of large clinical trials have been initiated to assess therapeutic strategies to improve prognosis for patients with this condition. Results from one of the largest and most recently completed of such studies, the Studies of Left Ventricular Dysfunction (SOLVD) trial, demonstrate that addition of the long-acting angiotensin-converting enzyme (ACE) inhibitor, enalapril to conventional therapy with diuretics and digoxin is associated with reduced rates of mortality and hospitalization for heart failure. Activation of the renin-angiotensin-aldosterone system (RAAS) appears to play an important role in the pathogenesis of this condition. The effects of treatment with this ACE inhibitor may be related to the degree of RAAS suppression it affords.