We report a case of a 44 year old femele with unilateral aldosterone-proudcing adrenal adenoma characterized by hypertension, plasma aldosterone excess, and low plasma renin, commonly but not invariably with hypokalemia. She also had asymmetric septal hypertrophy of left ventricle established with two-dimensional echocardiography. The electrocardiogram showed inverted T wave and prominent U wave with high QRS voltage on precordial leads. In the case of this patient, we are not sure whether asymmetric septal hypertrophy was caused by secondary hypertension and chronic aldosterone excess of primary aldosteronism, or hypertrophic cardiomyopathy per se, so further long=term follow-up is required to determine it. Following the successful unilateral adrenalectomy, however, the systemic pressure fell down to the normal level and electrolyte abnormalities were corrected immediaterly within a few days and the modest regression in septal hypertrophy was noted in one year, suggesting that the promary aldosteronism contributes to the development or porgression of asymmetric septal hepertrophy.