Autoradiographic and biochemical analyses of the hearts of female rhesus monkeys and baboons indicate that atrial and ventricular myocardial cells contain androgen receptors. Although the specific effects of nuclear uptake and retention of androgen on the function of heart muscle cells are not known, the presence of this receptor suggests that sex steroid hormones may affect myocardial function directly and may explain some of the peculiar differences in heart disease between men and women.