SummaryThree patients in the same family with Addison's disease were reported. Six others in this family died of similar Addison's disease symptoms. These nine patients were all male. Therefore, genetically an X‐linked inheritance was most probable.Detailed endocrinological examinations on these three patients were performed. Especially we observed the changes of the renin‐angiotensin system in Addison's disease. The plasma renin activity levels in these patients were high and suppressed by the administration of sodium chloride, Cortisol, and 9α‐fluorohydrocortisone.The blood pressure and secretion of aldosterone were little influenced by the administration of angioten