Persistent hypercalcemia after cervical exploration for suspected primary hyperparathyroidism is rare. In this retrospective review, some lessons and pitfalls have been emphasized--knowledge that should minimize this occurrence. There is no better lesson than experience. We concur with Van Vroonhoven and Muller that, in most instances, failure of the primary operation is unnecessary. This is supported by our review, in which 500 patients underwent exploration for primary hyperparathyroidism, 95 per cent of whom were rendered normocalcemic postoperatively, with minimal postoperative morbidity and an operative mortality of zero per cent.