The use of the antithyroid drugs (ATD) has been frequently questioned during the last years because of the high rates of relapses (about 50% in the overall statistical evaluations). Nevertheless, in terms of euthyroidism, the results obtained with the three main treatments (radio-iodine, surgery and ATD) are approximately similar. Recently, a new interest for ATD has been suggested when their immunosuppressive effects were proven by in vitro assays. In vivo, the immunosuppressive properties of ATD remain a matter of controversy; in fact the usual doses do not correspond to those needed to obtain the in vitro effects. In the near future, some trial will determine if the high doses of ATD actually improve the long-term results obtained with this therapy.