SUMMARYOleic acid uptake and esterification in intact intestinal mucosa were studied in 14 infants and children with chronic non-specific diarrhea, but histologically normal small intestinal mucosal biopsies, using an in vitro technique. The uptake rate was 5.876 ± 1.942 nmol fatty acid/mg Nitrogen/minute and the esterification rate was 4.060 ± 1.010 nmol fatty acid/mg Nitrogen/minute, comparable to previous adult esterification studies. No effect of age on either esterification or uptake was present. Mucosal injury resulted in significant reductions in esterification (p < 0.001) and uptake (p < 0.05) compared to controls. Bile acid deficiencies led to reductions in mucosal esterification (p < 0.05) but not uptake.SPECULATIONThe intestinal mucosal biopsy has been an invaluable tool in the study of the histopathology and ultrastructural pathology of human disease; it will become a valuable tool to study intestinal biochemistry, enzymblogy and physiology. The simplein vitroincubation technique described, with application to the study of fatty acid uptake and esterification and to other areas of mucosal metabolism, may allow delineation of new etiologies for chronic infantile diarrhea. Specific alterations in mucosal metabolism may be found associated with alterations in intestinal mucosa morphology or intraluminal conditions.