When dysfunction of two or more endocrine glands occurs in association with circulating organ specific antibodies directed against the involved glands, the term polyglandular autoimmune (PGA) syndrome is applied. This syndrome is usually classified into three groups. The autoimmune nature of this disease has been based on the presence of lymphocytic infiltration of the affected glands, organ specific autoantibody in serum, cellular immune defects and association with HLA DR/DQ genes. A 12-year-old girl developed PGA syndrome, type III manifesting Grave's disease and insulin-dependent diabetes mellitus. The thyroid microsomal Ab, TSH receptor Ab and pancreatic islet cell Ab were positive. She should be observed for the possible development of adrenal insufficiency and/or other autoimmune disease.