The surgical approach to differentiated thyroid carcinoma is still controversial, as many authors consider it necessary to remove the whole gland. Therefore, when definitive histological diagnosis is made following limited resection, reoperation and completion thyroidectomy (CT) is sometimes recommended. The main indications are for follicular cancer or for patients with a carcinoma of > or = 1 cm previously treated with lobectomy or limited resection (early CT), or for local recurrence after previous treatment (late CT). Several authors, however, draw attention to the high rate of complications following completion thyroidectomy and advocate its use in more limited circumstances. The aim of the study was to evaluate the results of our experience with CT in the National Cancer Institute in Naples. Of 131 patients treated for thyroid cancer 35 (26.7%) underwent a CT. Re-operation was performed within 6 months in 26 cases (74.3%) and later in the remaining nine cases (25.7%): carcinoma in the residual gland was found in six cases (23%) of early CT, and in four cases (45%) in the late CT group with an overall incidence of 28.5%. Post-operative complications were: transient hypoparathyroidism, two cases (5.6%), permanent in one (2.8%). Transient recurrent laryngeal nerve palsy occurred in three patients (8.5%) and became permanent in one case (2.8%). Completion thyroidectomy can therefore be considered a safe procedure.