A 56-year-old man was admitted to the hospital because of acute putative cholangitis with septic shock and acute renal failure (ARF). Examination on admission did not display any disorder of calcium metabolism. Intensive care including continuous arteriovenous hemofiltation (CAVH) enabled to perform radical operation on 12th hospital day. Postoperatively he underwent CAVH for ARF land showed hypercalcemia (15.2 mg/dl) at the phase of recovery from acute renal failure. Serum PTH level elevated to 5.1 ng/ml at the same time. Despite of improvement of general condition, significant symptoms related to hypercalcemia including restlessness, distraction, thirsty and fatigue were revealed. Administration of elcitonin and washout therapy were effective for the treatment of hypercalcemia. However, symptoms of hypercalcemia persisted. On several examinations a left parathyroid tumor over 1 cm in diameter which was causative of hypercalcemia was found. On 93rd hospital day, the tumor was extirpated. It was histologically diagnosed as eosinophilic adenoma. Laboratory data and neurological condition hecame to normal on the next day. In present case a parathyroid adenoma, existed previously on admission, was probably stimulated during ARF and induced hypercalcemia. With a progression of emergency treatment, further increase in patients with renal failure who are treated for a longer period can be considered, when strict observation of the parathyroid function would be necessitated.