ABSTRACT.Ten patients, who developed postenteritis enteropathy with chronic diarrhoea, failure to thrive and small intestinal mucosal damage after an episode of acute gastroenteritis, were studied prospectively. All patients experienced severe growth retardation. Maximum deviation of height and weight from mean values of age‐correlated normal children were −1.7 and −3.1 SD (median values), respectively, as compared to −0.1 and 0 SD before onset of the illness. One child died after 14 months of illness. The long‐term outcome was satisfactory for the 9 surviving children. For these children, treatment with an elemental diet (in some cases supplemented initially with parenteral nutrition) and later a lactose‐free diet lead to resolution of diarrhoea within periods ranging from 0.5 to 10 months. The phase of catch‐up growth lasted from 4 to 36 months, resulting in final height and weight deviating −0.6 and −0.8 SD (median values), respectively, from normal mean values. Attempt to predict duration of diarrhoea or length of catch‐up growth phase by means of age, weight before illness, characteristics of small intestinal biopsy or maximum deviation of height or weight were unsuccessful. The incidence of postenteritis enteropathy for children of North European ethnic origin was estimated to be 7.6/1000000 children below 7 years of age/year, corresponding to 1.2/1000 children hospitalized for ac