Rapid identification of parathyroid tissue has been rendered possible by preoperative intravenous infusion of methylene blue before exploration of the neck. The technique has been used on 17 patients with thyroid and parathyroid disorders. In all cases one or more of the parathyroids have been demonstrated with histological confirmation, but with greater experience almost all have been shown readily. This has resulted in an appreciable reduction in operating time, and the method should help to reduce the high incidence of clinical hypoparathyroidism after total thyroidectomy.