It has been established that Grave's disease is an autoimmune condition characterized by immunization against TSH receptors. Neither the receptors nor the stimulating immunoglobulins have been identified, but there seems to be two types of antireceptor antibodies: some stimulate the production of hormones or of thyroid stimulating immunoglobulins (TSI) and are responsible for thyrotoxicosis; others stimulate cell proliferation or thyroid growth immunoglobulins (TGI) and account for the diffuse goitre. The mechanism that triggers off autoimmunization is still unknown, but the disease frequently occurs in individuals genetically predisposed, as suggested by the high incidence of some HLA B8 and DR W3 antigens.