The chance of permanent remission after prolonged drug therapy was investigated in 41 patients with toxic multinodular goiter. For purposes of comparison a group of 41 patients with Graves' disease was also studied. After euthyroidism was achieved all patients received a combination of thionamide and thyroxine for at least 12 months. The minimum follow-up period was 2 yr. Relapse of thyrotoxicosis occurred in 95.1% of patients with toxic multinodular goiter and 34.1% of patients with Graves' disease (p < 0.001). It is concluded that for patients with toxic multinodular goiter early radioiodine therapy or surgery is preferred since prolonged drug therapy seldom produces permanent remission.