A 39-yr-old woman, who had been treated for Behcet's disease for 4 yr, was admitted for further investigation of recently identified hypokalemia and hypertension. Suppressed plasma renin activity with elevated plasma aldosterone concentration and an anomalous postural decrease in plasma aldosterone were observed. An abdominal CT scan revealed a right adrenal mass. The patient was diagnosed with Conn's syndrome. The association of Conn's syndrome with Behcet's disease was thought to be coincidental. To our knowledge, this is the first case of Conn's syndrome associated with Behcet's disease.