The choice of treatment for hyperthyroidism should be preceded by considering: (a) whether the diagnosis is correct; (b) the severity of the disorder; (c) the cause of the thyroid hormone excess; (d) factors such as patient age, size of goitre, associated diseases, previous treatment, and (e) patient preference. If hyperthyroidism appears to be severe, a judgement based on clinical rather than biochemical features, there is generally no safe alternative to the initial use of a drug from the thioamide thioureylene group (carbimazole, methimazole or propylthiouracil) to make the patient euthyroid as rapidly as possible. There are numerous different schedules for the use of these drugs, alone or in conjunction with surgery, radioactive iodine, or drugs such as beta-blocking agents, iodide or thyroxine. Patients can be made euthyroid with reasonable certainty, but an underlying abnormality often remains. The patient's understanding of the natural history of his or her condition is crucial in achieving adequate follow-up.