American College of Cardiology/American Heart Association class I recommendations for treating patients with heart failure (HF) and abnormal left ventricular ejection fraction are diuretics in patients with fluid retention, an angiotensin-converting enzyme (ACE) inhibitor unless contraindicated, a beta-blocker unless contraindicated, digoxin for the treatment of symptoms of HF, and withdrawal of drugs known to precipitate or aggravate HF such as nonsteroidal anti-inflammatory drugs, calcium channel blockers, and most antiarrhythmic drugs. Class II(a) recommendations for treating HF with abnormal left ventricular ejection fraction are spironolactone in patients with class IV symptoms, preserved renal function, and normal serum potassium; exercise training as an adjunctive approach to improve clinical status in ambulatory patients; an angiotensin receptor blocker in patients who cannot be given an ACE inhibitor because of cough, rash, altered taste sensation, or angioedema; and hydralazine plus nitrates in patients being treated with diuretics, a beta-blocker, and digoxin who cannot be given an ACE inhibitor or an angiotensin receptor blocker because of hypotension or renal insufficiency. Patients with diastolic HF should be treated with cautious use of diuretics and with a beta-blocker. An ACE inhibitor should be added if HF persists or an angiotensin receptor blocker if the patient cannot tolerate an ACE inhibitor because of cough, angioedema, rash, or altered taste sensation. Isosorbide dinitrate plus hydralazine should be added if HF persists. A calcium channel blocker should be added if HF persists. Digoxin should be avoided in diastolic HF if sinus rhythm is present.