From 1950 to 1965, 285 thyroidectomies were performed for hyperthyroidism with no deaths and few complications unless the patient had a repeat thyroidectomy. Total thyroidectomy and total lobectomy did not affect the incidence of complications. Seven percent of patients developed recurrent hyperthyroidism and 25% developed hypothyroidism. The latter occurred within a few months after thyroidectomy and did not increase progressively in the late posttreatment period as occurs after radioactive iodine ( 131 I) therapy. Postoperative thyroid function and the histopathology of the surgical specimen were compared. Although there was some correlation between lymphocytic infiltration and the development of hypothyroidism, this correlation was not consistent. We have concluded that subtotal thyroidectomy is safe and effective treatment in patients who have not had previous thyroid surgery. Because of the higher risk of postoperative complications after repeat thyroidectomy, 131 I therapy is advised for recurrent hyperthyroidism.