Iron deficiency is commonly seen in congestive heart failure (CHF) in both anemic and nonanemic patients. In six studies in which these iron-deficient patients with CHF were treated with intravenous (IV) iron, five found an improvement in the hemoglobin. In uncontrolled and controlled studies, the New York Heart Association (NYHA) class, quality of life, and exercise capacity were improved consistently with IV iron. In some studies, cardiac function also was improved. In one large, double-blind, placebo-controlled study of IV iron, the patient global assessment, quality of life, and NYHA class improved rapidly in both those who were anemic or not anemic. In contrast to these studies, another controlled study of anemia in CHF showed no effect of oral iron on hemoglobin or on any cardiac parameters over 1 year. These studies suggest that CHF in both anemic and nonanemic iron-deficient patients may benefit from a course of IV iron, but not oral iron.