Children with ileal resection/dysfunction since infancy have bile that is not supersaturated with cholesterol. Five sexually mature subjects (age 16-19 years) who had been previously investigated in childhood (age 4-9 years) were studied. Gallstones were found in one. Bile rich duodenal aspirates were analyzed for lipid content (molar fraction) and the cholesterol saturation index was calculated. In the postpubertal subjects, a significantly higher proportion of biliary cholesterol (22.0% +/- 4.8% vs. 3.2% +/- 0.6% and 5.7% +/- 0.5%, P less than 0.005) and significantly lower bile acids (58.1% +/- 3.9% vs. 79.7% +/- 2.3% and 78.2% +/- 1.9%, P less than 0.005) were found compared with the initial (prepubertal) samples or in samples from 20 healthy young adults. The cholesterol saturation index was significantly higher (3.1 +/- 0.7 vs. 0.6 +/- 0.1 and 1.1 +/- 0.1, P less than 0.005) whereas phospholipid content did not change (19.9% +/- 1.6% vs. 17.1% +/- 1.8% and 16.6% +/- 1.6%) as compared with themselves before puberty and as healthy young adults, respectively. It was concluded that children with ileal resection/dysfunction do not appear at risk for cholesterol cholelithiasis before puberty; however, the development of biliary cholesterol supersaturation after puberty may predispose them to gallstone formation in adulthood.