Obesity can result in alterations in cardiac structure and function even in the absence of systemic hypertension and underlying organic heart disease. Increased total blood volume creates a high cardiac output state that may cause ventricular dilatation and ultimately eccentric hypertrophy of the left (and possibly the right) ventricle. Eccentric left ventricular (LV) hypertrophy produces diastolic dysfunction. Systolic dysfunction may ensue due to excessive wall stress if wall thickening fails to keep pace with dilatation. This disorder is referred to as obesity cardiomyopathy. The presence of systemic hypertension in obese individuals facilitates development of LV dilatation and hypertrophy. Congestive heart failure may occur in such individuals, and may be attributable to LV diastolic dysfunction or to combined LV diastolic and systolic dysfunction. The sleep apnea/obesity hypoventilation syndrome occurs in 5% of morbidly obese individuals and is potentially life-threatening. Treatment of obesity cardiomyopathy consists of weight loss, salt restriction, and diuretics. Digitalis and vasodilators may be useful in selected cases. Central obesity is probably a risk factor for the development of coronary heart disease. Alterations in lipid and insulin metabolism may facilitate development of coronary heart disease in obese patients.