A 32-year-old man undergoing haemodialysis treatment for 10 years was referred to our hospital because of intractable heart failure with atrioventricular block. On the 5th hospital day he was found dead in bed. Autopsy revealed extensive metastatic calcification involving the myocardium and the cardiac conduction system, and a parathyroid adenoma with hyperplastic parathyroid glands. Retrospectively, first-degree heart block developed 14 months before death, and was subsequently associated with intraventricular conduction defect and atrioventricular block (Wenckebach type). Throughout the 3 years the patient received 1 alpha-hydroxycholecalciferol (1 alpha-OH-D3) and the calcium-phosphorus product (Ca X P) exceeded 70. 1 alpha-OH-D3 should not be prescribed when patients develop an increase in Ca X P and exploration of the parathyroid glands should not be delayed if heart block presents in long-term haemodialyzed patients.