Since theraphy of Graves' disease is not directed towards the cause of the disease, medical theraphy is still the first choice and symptomatically effective in treating hyperthyroidism. Antithyroid drugs are effective in restoring euthyroidism in> 90% of the patients durning 4-6 weeks, but 30-50% of the patients experience relapse after withdrawal. Previous prospective randomized studies evaluated prognostic parameters and the use of levothyroxine for prevention of relapse of hyperthyroidism. Recent studies have addressed the period after withdrawal amd focused on the natural course of disease. The results of a recent prospective randomized and controlled multicenter study were as follows: supplementation of levothroxine does not prevent relapse of hyperthyroidism. Basal TSH (4 weeks after withdrawal of antithyroid drugs) is the best prognostic marker. Smoking and positive TSH-receptor-antibodies at the end of antithyroid theraphy are other risk factors.