Twenty-one patients in a series of 283 treated surgically for primary hyperparathyroidism between 1960 and 1982, underwent reoperation. Eleven had been previously treated elsewhere. The initial cervicotomy was negative in fourteen cases, but had led to the ablation of one or more adenomas in seven. The reason for reoperation was recurrence or persistence of hyperparathyroidism (HPT). It was commenced by cervicotomy in the eleven patients initially treated elsewhere, and by cervicotomy and/or sternotomy for the others. Reoperation involved ablation of adenomas in thirteen cases, but was negative in the remaining eight. Three of the eight underwent a second reoperation, with success in two cases. Overall, reoperations led to ablation of sixteen adenomas in fifteen patients. Ten adenomas were ectopic, including eight located mediastinally . Ten sternotomies were performed, leading to ablation of four mediastinal adenomas. Postoperative complications included five recurrent paralyses and two severe cases of hypocalcemia. One patient with parathyroidal carcinoma died of malignant hypercalcemia. Fifteen of the twenty one patients (71%) were cured of their HPT. Basing themselves on these cases, and a review of the literature, the authors describe the indications and practical management of reoperative surgery for primary HPT.