All the patients with clinical evidence of MTC have raised basic level of plasmatic calcitonin. Low prevalence of patients with MTC between those with thyroid nodules makes unpractical calcitonin level determination as a screening test. Fine – needle aspirate biopsy has to be routinely used for patients with thyroid gland nodules. The suspicious for MTC is confi rmed afterwards by imunohystochemical test for calcitonin, combined with plasma calcitonin level. The second step in MTC is stadium determining. MRI and, in some cases USG, are used for adenopathy or local invasion appreciation. CT or MRI of the lung and mediastinum are useful in fi nding etastases spreading. Implication of hereditary factors is the 3-rd step in MTC diagnosis. MTC treatment is complex and implies surgery, radiotherapy, hormonotherapy and chemotherapy sometimes.