The rapid parathyroid hormone assay (rPTH) is an effective tool in minimally invasive resections of parathyroid adenomas. However, there are relatively few reports examining its utility in the full spectrum of parathyroid disease. The purpose of this study was to examine the utility of the rapid parathyroid hormone assay in uniglandular, multiglandular, and recurrent hyperparathyroidism. A retrospective analysis of all patients undergoing parathyroid resection from June 2001 to March 2003 was undertaken. All patients underwent preoperative localization studies. Rapid parathyroid hormone (PTH) levels were drawn immediately prior to and 10 minutes following parathyroid resection. A decline of > or = 50 per cent rPTH qualified as a successful/complete resection. Additional intraoperative samples were drawn as needed for patients with multiglandular disease. Of 46 treated patients who were examined (average age, 54 years), 30 had single, 12 patients had multigland disease, and 4 had recurrent/persistent hyperparathyroidism. Thirty-seven patients had primary hyperparathyroidism (32 with single and 3 with double adenomas; 2 with hyperplasia), 4 patients had secondary hyperparathyroidism, and 5 tertiary hyperparathyroidism. All procedures were considered successful, as every patient exhibited a postresection decrement in rPTH exceeding 50 per cent (average decrement, 91%). Although 2 patients exhibited a postoperative PTH increase exceeding 50 per cent of the preoperative value, all remained asymptomatic and eucalcemic (median follow-up, 21.5 months). The rPTH assay is an effective tool in determining success of parathyroidectomy in patients with primary uni- and multiglandular as well as recurrent hyperparathyroidism. It can be used to achieve minimally invasive neck dissections or guide surgical decision-making in more complex cases.