As an aid to diagnosis in a patient with neonatal hyperthyroidism, a thyroid99mTc sodium pertechnetate scan was performed. This demonstrated the diffusely enlarged gland typical of Graves’ disease with a gland uptake in the hyperthyroid range. Thein-vivo thyroid scan gives immediate diagnostic information and under appropriate conditions delivers to the neonatal thyroid a radiation dose comparable to that delivered by a plain chest x-ray.