Three cases of X-linked auto-immune enteropathy with haemolytic anaemia and polyendocrinopathy are described from one related Japanese kindred. Two boys had died due to severe diarrhoea accompanied by total or subtotal intestinal villous atrophy. In contrast, although one patient showed the same symptoms and had circulating IgG antibodies against enterocytes, his condition improved dramatically and he developed well following the use of cyclosporin A (CSA). CSA may be beneficial in patients with this rare disorder. Auto-immune enteropathy should be considered as a cause of protracted diarrhoea with unknown aetiology.