OBJECTIVE: Because hypoparathyroidism is a serious complication of thyroidectomy, we attempted to elucidate factors determining the risk of this postoperative outcome. SETTING: Four tertiary care hospitals in Albuquerque, New Mexico. PATIENTS: A retrospective study of 142 patients who underwent total or subtotal thyroidectomy between 1988 and 1995. MEASUREMENTS AND MAIN RESULTS: Permanent hypoparathyroidism was defined as hypocalcemic symptoms plus a requirement for oral vitamin D or calcium 6 months after thyroidectomy. Factors analyzed to determine their contribution to the risk of persistent postoperative hypoparathyroidism were the indication for thyroidectomy, performance of a preoperative thyroid needle biopsy, type of surgery, postoperative pathology, presence and stage of thyroid carcinoma, resident surgeon involvement, and specialty of the surgeon performing the procedure. Surgical specialty and stage of thyroid carcinoma were independent risk factors for persistent postoperative hypoparathyroidism by multivariate analysis. Nine (29%) of 31 patients who had thyroidectomy by otolaryngologists met criteria for permanent hypoparathyroidism, and 6 (5%) of 111 patients who had thyroidectomy by general surgeons met the same criteria (  p < .001). Adjustment for the effect of stage did not eliminate the effect of specialty (  p= .006), and adjustment for the effect of specialty did not eliminate the effect of stage (  p= .02), on the occurrence of postoperative hypoparathyroidism. CONCLUSIONS: We conclude from our data that patients undergoing thyroidectomy by an otolaryngologist may be at a higher risk of permanent postoperative hypoparathyroidism than patients who undergo thyroidectomy by a general surgeon. This may reflect differences in case selection or surgical approach or both. KEY WORDS: thyroidectomy; surgical complications; hypoparathyroidism; hypocalcemia; thyroid carcinoma.