Crataegus monogyna Jacq (Lindm), C laevigata (Poir) DC, or related Crataegus species, collectively known as hawthorn, have been used in the treatment of cardiovascular diseases. Clinical studies have found that standardized extracts show promise as adjunctive agents for the treatment of left ventricular dysfunction. Other trials consistently demonstrate its ability to improve exercise tolerance and symptoms of mild to moderate heart failure. Preliminary evidence indicates that it improves left ventricular performance, as measured by ejection fraction. In order to properly use hawthorn in the treatment of heart failure, a large, controlled, multicenter trial in which mortality serves as the primary endpoint is needed.