Heart failure is a common, progressive, complex clinical syndrome with high morbidity and mortality. Coronary artery disease is its most common cause. The evaluation of symptomatic patients with suspected heart failure is directed at confirming the diagnosis, determining the cause, identifying concomitant illnesses, establishing the severity of heart failure, and guiding therapy. The initial evaluation should include a focused history and physical examination, a chest radiograph, and an electrocardiogram. The presence of heart failure can be confirmed by an echocardiogram. Heart failure is highly unlikely in the absence of dyspnea and an abnormal chest radiograph or electrocardiogram. Radionuclide angiography or contrast cineangiography may be necessary when clinical suspicion for heart failure is high and the echocardiogram is equivocal. Patients with confirmed heart failure should undergo additional testing, including a more detailed history and physical examination; a complete blood count; blood glucose measurement; liver function tests; serum electrolyte, blood urea nitrogen, and creatinine measurements; lipid panel; urinalysis; and thyroid-stimulating hormone level. A serum ferritin level, human immunodeficiency virus test, antinuclear antibody assays, rheumatoid factor test, or metanephrine measurements may be required in selected patients. Patients with coronary artery disease, hypertension, diabetes mellitus, exposure to cardiotoxic drugs, alcohol abuse, or a family history of cardiomyopathy are at high risk for heart failure and may benefit from routine screening.