The clinical features and management of 90 thyrotoxic and 11 euthyroid patients with a single autonomous hot nodule in the thyroid have been reviewed to assess the results of surgery and radio-iodine therapy. Symptoms and signs of thyrotoxicosis were often minimal but histories were frequently long with cardiac complications predominating. Thyrotoxicosis was permanently eradicated in the 60 patients treated surgically, although hypothyroidism occurred in 6.6 per cent. Twelve of the 37 (32 per cent thyrotoxic patients receiving radio-iodine needed further definitive treatment for persistent or recurrent thyrotoxicosis, but only 2 patients (5 per cent) became hypothyroid. Early surgery for the autonomous toxic thyroid nodule ensures control of the thyroid overactivity and minimizes the risk of permanent cardiac damage. The absence of morbidity justifies surgical excision of autonomous hot nodules in patients who are euthyroid to eliminate the risk of thyrotoxicosis supervening.