The frequency and significance of cervicomediastinal lymph node metastases have been investigated in 82 medullary thyroid carcinoma (MTC) patients retrospectively comparing two surgical techniques of lymph node dissection: selective lymphadenectomy (n = 63) versus compartment-oriented microdissection (n = 35). No positive correlation was observed between primary tumor size and the number of lymph node metastases. In patients with lymph node metastases proven histologically, 42% showed only cervical involvement (35% unilateral--type A, 7% bilateral--type B) and 22% cervicomediastinal lymph node involvement (15% cervico-unilateral and mediastinal--type C, 7% cervicobilateral and mediastinal--type D). Biochemical cure was 83% in node-negative patients but only 21% in node-positive patients. In node-positive MTC, calcitonin normalization was achieved in none with bilateral lymph node involvement but only in those unilateral lymph node metastases (31% in type A, 17% in type C). Survival and biochemical cure are significantly improved by application of the compartment-oriented microdissection method more so at primary surgery than at reoperation.