Intraluminal tumor thrombus in great cervical veins as a result of thyroid carcinoma is extremely rare. Three patients (2 Hurthle cell, 1 papillary carcinoma) were surgically treated for thyroid carcinoma associated with tumor thrombus in the great cervical veins. Tumor thrombus in the internal jugular vein due to extension of thyroid carcinoma was found in these 3 patients. Segmental resection of the internal jugular vein was performed in all cases and a tumor thrombectomy from subclavian vein was accomplished in 1 patient. Histological examination verified intraluminal tumor thrombus resulting from invasion of thyroid carcinoma in all patients. The postoperative follow-up period ranged from 1 to 2 years. Of 2 patients undergoing completion thyroidectomy, 1 died of distant metastasis, the other underwent reoperation for local recurrence. The patient who had a definitive primary surgical procedure is free of recurrence. Appropriate initial surgical procedure in rare cases of thyroid carcinoma associated with intraluminal tumor thrombus in great cervical veins seems to improve the clinical outcome of the disease.