Aim and objective The incidence and risk factors for permanent hypocalcemia in thyroid carcinoma were investigated. Materials and methodsThe records of 417 patients were reviewed retrospectively at tertiary oncology referral center. Total or subtotal thyroidectomy patients constituted group I (n = 225), reoperative thyroid surgery patients constituted group II (n = 106), and therapeutic neck dissection cases constituted group III (n = 86). Age, gender, thyroid functions, pathologically verifi ed tumor type, differentiation, localization and size, multicentricity, thyroid capsule invasion, extrathyroidal soft tissue invasion, coexistence of lymphocytic thyroiditis, metastatic lymph nodes dissected, incidental parathyroidectomy, and the type of surgery were investigated.Re sults Permanent hypocalcemia was seen in 32 (7.7%) patients. The incidence of permanent hypocalcemia for each group was 1.7%, 10.3% and 19.7%, respectively. Related risk factors were hyperthyroidism for group I [adjusted relative risk (RR) = 21.1, 95% confi dence interval (CI) = 2.6-165, p = 0.01] incidental parathyroidectomy for group II (RR = 7.8, 95% CI = 1.9-31.0, p = 0.004), and extrathyroidal soft tissue invasion (RR = 3.1, 95% CI = 1.1-9.5, p = 0.03) for group III.Conclusion Permanent hypocalcemia rate was increased with reoperative thyroid surgery and neck dissection added to total thyroidectomy. Hyperthyroidism, incidental parathyroidectomy and extrathyroidal extension were related risk factors.