Drugs can affect thyroid functional status in numerous ways. They may influence thyroid homeostasis at any level from their synthesis, secretion, transport or end-organ action resulting in hypothyroidism or hyperthyroidism. Amiodarone is an important drug in this group. The effects of amiodarone on thyroid function result from iodine release and intrinsic drug properties. Both amiodarone-induced thyrotoxicosis (AIT) and amiodarone -induced hypothyroidism (AIH) may develop in apparently normal thyroid glands or in glands with preexisting, clinically silent abnormalities. Treatment of AIH consists of thyroxine replacement while continuing or discontinuing amiodarone therapy. In type I AIT the main medical treatment consists of simultaneous administration of thionamides and potassium perchlorate, while in type II AIT, glucocorticoids are the most useful therapeutic option. It is important to evaluate patients before and during amiodarone therapy. The list of drugs affecting thyroid function is long with new drugs being added. Some of them are clinically important while others just produce diagnostic dilemmas. The possible effect of drugs on the results of thyroid-function tests should always be considered while making decisions regarding patient care.