A retrospective analysis of 21 patients with jejunal atresia and 24 with ileal atresia showed more differences than similarities between the two categories. The incidence of jejunal atresia appeared to be increasing during the period of observation (1978 to 1987). In the past 2 years, many children with jejunal atresia, who belonged to a set of heterozygotic twins, were admitted to this institution. The mean birth weight and gestational age in jejunal atresia were significantly lower than in ileal atresia. The majority of jejunal atresias were multiple, whereas most ileal atresias were single. Antenatal perforation occurred rather frequently (10 cases) in ileal atresia but only twice in jejunal atresia. The postoperative course was more often prolonged in jejunal than in ileal atresia. Mortality was higher in jejunal atresia: three deaths, all in apple peel atresia, versus one death in ileal atresia. An explanation for some of these observations can be found in a difference of compliance of the bowel wall between jejunum and ileum: the more compliant jejunal wall allows for massive dilatation with subsequent loss of peristaltic activity. It is postulated that because of the many differences, jejunal and ileal atresia may be considered as separate diseases.