Autoimmune polyglandular syndromes (APS) are conditions characterized by the association of two or more organ-specific disorders. Type 2 APS is defined by the occurrence of Addison's disease with thyroid autoimmune disease and/or Type 1 diabetes mellitus. Clinically overt disorders are considered only the tip of the autoimmune iceberg, since latent forms are much more frequent. Historical, clinical, genetic, and immunological aspects of Type 2 APS are reviewed. Furthermore, data on 146 personal cases of Type 2 APS are also reported.