Poorly differentiated insular thyroid carcinoma is classified as a separate entity among other tumors of the thyroid gland. Its histological pattern and clinical course are regarded as intermediate between well-differentiated and anaplastic thyroid cancer. The authors report Tc-99m pertechnetate, Tc-99m MDP and radioiodine imaging features in a 33-year-old male patient with metastatic insular carcinoma of the thyroid. The extent of involvement was almost identical in all three studies. Insular carcinoma of the thyroid was shown by biopsy, and the patient received a cumulative dose of 14,800 MBq (400 mCi) radioactive I-131. Other radionuclide imaging agents are also reviewed.