BACKGROUND: Completion thyroidectomy is the removal of any thyroid tissue that remains after a less than total thyroidectomy. This procedure has been commonly performed when the final histopathology of the excised ipsilateral thyroid lobe reveals papillary or follicular carcinoma of the thyroid. Complete thyroidectomy carries little morbidity if performed by experienced surgeons using a lateral approach. The purpose of this study is to reinforce the usefulness of a lateral approach. METHODS: A retrospective analysis over a 5 year period at the Department of Endocrine Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences (SGPGIMS) yielded 19 patients who underwent completion thyroidectomy. This group represents 23% of 82 patients who underwent total thyroidectomy for differentiated thyroid cancer (DTC) during that period. The residual thyroid tissue was excised through a lateral approach and could be resected safely, preserving the recurrent laryngeal nerve (RLN) and the parathyroid glands. RESULTS: A lateral approach dissection could be performed with ease in a virgin area. Excision of residual thyroid tissue could be performed safely even in cases with prior partial lobectomy or bilateral subtotal resection. Tumour was found in 52% of the re-operative specimens: in three out of four of those after a previous partial lobectomy, in six out of 12 of those after a total lobectomy, and in one out of three of those after a prior bilateral (although incomplete) thyroid resection. Postoperative complications included transient RLN palsy (n = 2) and transient hypoparathyroidism (n = 4). CONCLUSIONS: Completion thyroidectomy using a lateral approach is safe in re-operative thyroid surgery.