Rule and indications of lymph node dissection (LD) in thyroid carcinoma is still under debate because of the biological variety of different histological types and the difficulty to have an accurate preoperative diagnosis of metastatic lymph nodes; moreover prognostic factors of metastatic lymph nodes are still unclear. The AA. have separately analyzed different thyroid carcinomas and different clinical situations requiring thyroid LD. Metastatic lymph nodes from differentiated carcinomas, including papillary and follicular type, range from 12 to 90% and apparently do not worsen the prognosis. Level II-VI LD is indicated in presence of metastatic lymph nodes or macroscopic nodal recurrence after a previous LD. No prognostic advantages have been demonstrated when LD is performed without clinical or instrumental evidence of metastatic disease, including suspected recurrence characterised only by plasma Thyreoglobulin increased values. Lymph node metastases from medullary carcinoma range from 25 to 63%. Level II-VI LD is indicated if node metastases are present, whereas prophylactic LD, confined to level VI, is always recommended. Controversies still remain about: 1) LD extension whether it is prophylactic (level VI vs. II-VI) or in case of nodal involvement (levels II-VI monolateral or bilateral), 2) LD indications in case of an increased plasma Calcitonin levels during the follow-up after total thyroidectomy, without clinical or instrumental evidence of nodes involvement. Anaplastic carcinoma represents 5% of all thyroid carcinomas; it is the most aggressive type with an early tendency to invade surrounding organs and to give metastases; prognosis is very poor. LD is indicated only for a palliation in cases with compression syndromes.