To investigate the role of primary and/or secondary modified radical neck dissection (MRND) in patients with medullary thyroid carcinoma (MTC), follow-up data on 43 patients operated on between 1972 and 1983 were analyzed retrospectively; patients included 16 with sporadic MTC (group 1) and 27 with multiple endocrine neoplasia type 2 (group 2). Primary surgical therapy consisted of (near-) total thyroidectomy and limited lymph node dissection; one patient in group 1 and two in group 2 underwent primary MRND. Positive nodes were found in nine patients of group 1 and in 12 of group 2. Calcitonin (CT) was raised postoperatively in 11 group 1 patients, who all died (four after additional MRND). Postoperative CT was normal in the four survivors of group 1. In group 2, post-operative CT was raised in 15 patients, including those who had MRND and in four apparently node-negative patients. Three of them underwent additional MRND, which was successful in one case. One patient in this group died of the disease; two patients developed elevated CT levels during follow-up, whereas in one, CT normalized spontaneously. In conclusion, the role of extensive lymph node surgery in patients with more than limited lymph node involvement or elevated postoperative CT levels remains to be established.