We describe a 60-year-old patient with adrenal insufficiency and hypothyroidism who experienced syncope as a result of polymorphic ventricular tachycardia associated with long QT intervals. The deep inverted T waves and long QT intervals were normalized about 8 weeks after starting steroid replacement therapy. Although there have been some reports on electrocardiographic abnormality or polymorphic ventricular tachycardia in patients with adrenal insufficiency, the pathogenesis remains unknown. Hormonal disorders should be considered as a cause of polymorphic ventricular tachycardia associated with long QT intervals, even if plasma electrolyte levels are normal, because life-threatening arrhythmia is treatable by supplementation of the hormone that is lacking.