OBJECTIVE: To report a sequential occurrence of life-threatening hypokalemia and rebound hyperkalemia following barbiturate coma therapy. CASE HISTORY: A 53-year-old man was admitted to the division of nephrology due to sudden development of severe hypokalemia. The patient had been treated following a clinical diagnosis of traumatic subarachnoid hemorrhage and subdural hematoma. Barbiturate coma therapy had been performed on this patient. He developed fatal hypokalemia 10 hours after the start of thiopental administration which did not respond to potassium supplementation.