There are great differences in causes and treatments of hypoparathyroidism between patients with normal renal function and those with impaired renal function (dialysis patient). In patients with normal renal function, hypocalcemia and hyperphosphatemia develop because of the decrease in PTH synthesis or PTH function, and major target for treatment is hypocalcemia. In dialysis patients, hyperphosphatemia inevitably develops by the decrease in urinary excretion of phosphate and about three to six times greater concentration of PTH is required to maintain the normal bone metabolism. Hyperphosphatemia should be strictly treated, but it remains still unsure what is the real pathogenesis of hypoparathyroidism, and whether hypoparathyroidism should be treated or not in dialysis patient.