In Gabon, 15 children aged 13 to 36 months admitted for malnutrition with chronic diarrhea underwent a small bowel biopsy for detection of parasites in the duodenal contents and histologic evaluation of the intestinal mucosa. In every case, intraepithelial lymphocyte counts (IELC) were under the lower limit of normal for children and adults, regardless of whether or not parasites were found. Partial villous atrophy was a consistent finding. Proportion of lymphocytes among intraepithelial cells was 7.4 % in the 6 children with no parasitic infection, 7.9 % in the children with giardiasis, and 8.1 % in the children with strongyloidiasis. Appropriate treatment of the parasitic infections was quickly followed by resolution of the diarrhea in the nine patients with demonstrable intestinal parasites. These data should be compared with the well documented lymphocyte function anomalies associated with protein-calory malnutrition. The fall in IELC and lack of response to local anigenic stimulations are features of malnutrition.