The choice of treatment for thyrotoxicosis practised at the University Clinics, University of Helsinki, is reviewed. Patients below the age of 45-50 years with a small goitre (less than 50 g) are primarily treated with longterm antithyroid therapy, older patients with radioactive iodine. Recent observations on the absence of risks for thyroid carcinoma, leukaemia and genetic damage will probably change the impact of age on the use of radioactive iodine. Large diffuse goitres are operated on primarily, the second choice would be radioiodine. Nodular goitres, both multinodular and uninodular, are also operated on primarily the second choice being radioactive iodine. Postoperative recurrencies are always and recurrencies after longterm antithyroid treatment usually treated with radioactive iodine. Thyrotoxicosis during pregnancy is primarily treated with antithyroid drugs but if the goitre is very large or nodular and if large doses of antithyroid drugs are needed for adequate response, operation is recommended. In children the first choice is antithyroid therapy and the second one either operation or radioactive iodine depending on the size of the goitre.