Hypocalcemia following thyroid and parathyroid surgery is a well-recognized potential complication.To determine the utility of intraoperative quick parathormone assay in predicting severe hypocalcemia development following parathyroidectomy for a single-gland adenoma causing primary hyperparathyroidism.A retrospective cohort study was performed. IO-QPTH values were measured at time 0 (T0) before incision, and 10 (T10) and 30 minutes (T30) following excision of the hyperfunctioning gland. Percent decrease in IO-QPTH at 10 minutes (T10), maximum percent decrease of IO-QPTH value, and lowest actual IO-QPTH value obtained at surgery were used to determine any correlation with the development of postoperative hypocalcemia requiring treatment.Percent decrease in IO-QPTH at 10 minutes, maximum percent decrease in IO-QPTH and lowest IO-QPTH value did not correlate with the lowest postoperative calcium levels measured 18 hours after surgery (r = 0.017, P = 0.860; r = 0.018, P = 0.850; and r = 0.002, P= 0.985 respectively). For the purposes of our analysis, patients were subdivided into three groups. Group 1 comprised 68 patients with normal calcium levels (serum Ca 8.6-10.3 mg/dl), group 2 had 28 patients with hypocalcemia (8.1-8.6 mg/dl), and group 3 included 12 patients with severe hypocalcemia (calcium level < or = 8.0 mg/dl) requiring calcium supplementation due to symptoms of hypocalcemia. There was no difference between the three groups in the lowest IO-QPTH value (P = 0.378), percent decrease in IO-QPTH (P = 0.305) and maximum percent dercrease in IO-QPTH (P = 0.142).IO-QPTH evaluation was not useful in predicting the group of patients susceptible to develop severe postoperative hypocalcemia.