A neck mass in the right carotid triangle of a 28-year-old woman was found to be the only thyroid tissue she possessed. Resection of the mass led to clinical and biochemical hypothyroidism. A possible explanation for the unlikely occurrence of lateral aberrant thyroid tissue and absence of a thyroid gland in the usual location is offered. It is suggested that patients with midline or low lateral neck masses undergo isotopic scanning of the thyroid gland before any iodinated contrast materials are administered or surgery performed.