Immediate and persistent hypophosphatemia following subtotal parathyroidectomy, despite discontinuation of phosphate binders, developed in three chronic hemodialysis patients. Although the serum phosphorous level is regularly reduced by parathyroidectomy in such patients, prolonged hypophosphatemia has not previously been reported. This observation supports the concept that parathyroid overactivity in end-stage renal disease is a major determinant of hyperphosphatemia.