The cytotoxic T lymphocyte antigen-4 (CTLA4) gene on chromosome 2q33 encodes a key regulator in the adaptive immune system. The CTLA4 surface molecule is expressed on activated T lymphocytes and involved in down-regulation of the immune response. Previous studies on a possible association between autoimmune Addison's disease and CTLA4 polymorphisms have shown conflicting results. A recent study identified new candidate polymorphisms in the CTLA4 region, influencing gene splicing and thereby the relative abundance of soluble CTLA4. We genotyped 134 patients with Addison's disease and 413 healthy controls from Norway and United Kingdom for these newly identified polymorphisms. Our data demonstrate that the same polymorphisms that have recently been demonstrated to confer susceptibility to autoimmune thyroid disease and type 1 diabetes also confer susceptibility to Addison's disease. This finding suggests that polymorphisms in CTLA4 confer general risk to develop autoimmunity and identifies a potential therapeutic target in the prevention of autoimmune endocrine disorders.