Autoimmune thyroid diseases occur in subjects with genetic predisposition, and are responsible for a large spectrum of clinical manifestations. They have in common the presence of intra-thyroid lymphocytic infiltrate and serum antibodies against thyroid constituents. The main thyroid antigens are thyroglobulin (Tg), thyroperoxidase (TPO), thyrotropin receptor (RTSH) and sodium/iodide symporter (NIS) which has been recently cloned. The assays for antiTg and antiTPO antibodies have high specificity and sensitivity, but standardisation problems still exist. Second generation antiRTSH assays are now available. The discrimination between the stimulating and the blocking activities can been studied using cellular culture. The antiTPO antibodies are the more sensitive and the more specific diagnostic markers for autoimmune thyroid diseases but their use for therapeutic decision is limited. They are good predictive factors for a thyroid dysfunction during pregnancy, during amiodaron, lithium, and cytokines treatments. The antiTg antibodies search enables the validation of a Tg assay. The antiRTSH antibodies are precious tools for the diagnostic and the follow-up of Graves' diseases and fetal pathologies caused by the antibodies crossing over the placental barrier. The utility of antiNIS antibodies determination is not yet proved.