The gene responsible for autoimmune polyendocrino-pathy candidiasis ectodermal dystrophy (APECED) recently has been positionally cloned to 21q22.3. This novel gene, AIRE, encodes for a predicted 57.7 kDa protein featuring two PHD-type zinc fingers shared by other proteins involved in chromatin-mediated tran-scriptional regulation. APECED is an autosomal recessive condition characterized by multiple polyendocrinopathies, and the typical triad of APECED symptoms includes hypoparathyroidism, primary adrenocortical failure and chronic mucocutaneous candidiasis. The aetiology of APECED is linked directly to mutations within the coding region of AIRE. These mutations are predicted to lead to truncated forms of the protein lacking at least one of the PHD zinc fingers. In this study, we have investigated the sub-cellular localization of AIRE expressed transiently in COS cells and fibroblasts. We found that AIRE has a dual nuclear and cytoplasmic localization. The wild-type protein is directed to speckled domains in the nucleus and also shows co-localization with cytoskeletal filaments. N-terminal AIRE fragments deleted for the PHD domain show altered nuclear localization, suggesting that the APECED mutations may elicit their primary effects in the nucleus.