A surgical series of 30 cervico-mediastinal thyroid cancer patients operated on has been retrospectively reviewed. Results were compared with those obtained in patients operated on for benign cervico-mediastinal goiter and thyroid cancer confined to cervical region. Of 4688 thyroidectomies performed, 30 patients were operated on for thyroid carcinoma with cervico-mediastinal extension. There were 15 males and 15 females. The mean age was 67 years (range, 21-86 years). Patients with cervico-mediastinal cancer were significantly older than patients with benign cervico-mediastinal goiter (P < 0.0001). Time between onset of first symptoms and surgery was significantly longer in patients with cervico-mediastinal cancer than in those with benign cervico-mediastinal goiter (P < 0.0001) and cervical thyroid cancer. Signs and symptoms at the time of surgery were cervical mass in 28 patients (93%), cervical lymphadenopathy in 20 patients (66%), dyspnea in 21 (70%), dysphagia in 9 (30%), dysphonia in 2 (7%), and venous stasis in 1 (3%). None of the patients was asymptomatic. Total thyroidectomy with functional lymphectomy was performed in 16 cases. Seven of these patients were operated on in 2 stages. In 8 cases the operation was a debulking procedure, and in 6 it was a near-total thyroidectomy. Sternotomy was performed in two cases. A differentiated thyroid cancer was found in 21 patients (70%), medullary in 5 (17%) and undifferentiated in 4 (13%). The incidence of medullary carcinoma was significantly higher compared with cervical cancer (P < 0.008). Postoperative complications were higher than those occurring in benign cervico-mediastinal goiter and similar to those occurring in cervical cancer. The actuarial survival was similar to that of cervical cancer matched for age and sex. This analysis shows that the longer clinical history of goiter is related to its endothoracic development and its neoplastic transformation. This finding should further encourage surgeons to treat any cervico-mediastinal goiter as promptly as possible.