BACKGROUND Parathyroid carcinoma is rare, with a reported prevalence of 0.6% to 4.0% in patients presumed to have primary hyperparathyroidism. This study examines the long-term results of surgical therapy and combination chemotherapy. METHODS From 1938 to 1988, 1260 operations for primary hyperparathyroidism were performed; only six patients (0.47%) were subsequently found to have parathyroid carcinoma. A seventh patient was referred to our institution after the diagnosis of parathyroid carcinoma had been made. RESULTS All patients had excessive hypercalcemia (serum calcium concentration > 12.0 mg/dL) with a range of 12.3 to 18.3 mg/dL. Locally recurrent tumors causing recurrent hypercalcemia were managed by repeated neck exploration and tumor resection. Six of the seven patients (85%) survived 5 years, while four patients (57%) survived 10 years. CONCLUSIONS Diagnosis of parathyroid carcinoma rests upon postoperative surveillance of patients who have undergone previous neck exploration and resection of apparently benign adenomas. Long-term survival is possible with repeated resection of locally recurrent tumors.