A 60-year-old female received hemodialysis for 9 years in our dialysis unit. At the end of 1995, percutaneous ethanol injection therapy (PEIT) into the adenomatous parathyroid gland started due to severe secondary hyperparathyroidism. In the course of the PEIT, dyspnea gradually developed despite reduction of her dry weight. She was hospitalized for refractory congestive heart failure, at which time the diagnosis of hyperthyroidism due to Graves' disease was made. Therapy, 20mg of thiamazole every day for 1 month, resulted in improvement of heart failure after normalizing the thyroid function.We investigated the serum concentration of thiamazole to clarify the appropriate dose for patients with ESRD. The data showed its delayed absorption, prolonged half life and dialyzability. Based on these findings, we concluded that thiamazole should be administered to patients after dialysis with reduced doses in Graves' disease.