The triple A syndrome (MIM*231550) is a rare autosomal recessive disorder characterized by adrenocorticotropic hormone (ACTH) resistant adrenal failure, achalasia, alacrima and a variety of neurological and dermatological features. Adrenal insufficiency usually presents in the first decade of life, however in some patients it may occur later in life or may even lack completely. Recently, we and others identified a novel gene on chromosome 12q13, designated AAAS (Achalasia-Addisonianism-Alacrima-Syndrome gene) which is mutated in patients with triple A syndrome. We investigated n = 14 families including 111 patients with clinically suggested triple A syndrome and identified homozygous or compound heterozygous AAAS mutations in 78 families. Genotype/phenotype analyses revealed a highly variable occurrence, age of onset and severity of all clinical symptoms between patients with the same AAAS mutation. The obvious lack of a genotype/phenotype relationship is suggestive of modifying genes/factors which need to be determined. The AAAS protein function is unknown. With four WD repeats it belongs to the family of WD repeat-containing proteins which may exhibit a high degree of functional diversity. The subcellular localization of the protein and the determination of its putative binding partners will shed light on the role of the AAAS protein for the development and function of the adrenal gland and other neuroendocrine structures.