Background: Completion thyroidectomy is defined as the surgical removal of the remnant thyroid tissue following procedures less than total or near-total thyroidectomy. Although some authors advocate subtotal thyroidectomy with lower complication rates, total or completion thyroidectomy have been defended by others because of the improved survival and lower morbidity that is comparable with subtotal thyroidectomy. Objectives: The purpose of this paper is to review the necessity and safety of completion thyroidectomy for differentiated thyroid carcinoma(DTC). Materials & Methods: During the past 10 years(1986 to 1996) , authors have performed 211 total thyroidectomy. Ten of these patients were treated by completion thyroidectomy for DTC. Initial operation of 7 patients had been performed at St. Vincents Hospital and 3 patients at other hospital. The medical records of patients undergoing completion thyroidectomy were retrospectively reviewed. Results: The completion thyroidectomy specimen contained residual tumor cells in 8 of the 8 patients with papillary carcinoma and none of the two patients with follicular carcinoma. Complications of completion thyroidectomy were transient hypoparathyroidism in two patients and transient unilateral recurrent laryngeal nerve palsy in one patient. But permanent complications were not noticed. Conclusion: We recommend completion thyroidectomy as an efficient and safe method of surgical treatment with a low complication rate for DTC.