The enteric EPEC infection may cause different degrees of abnormalities in the small bowel villi. Morphological changes in the small intestine have been described in asymptomatic children who live in unfavourable environmental conditions. Enteric EPEC infections frequently occur in children living in such conditions and may worsen the already existing lesions. OBJECTIVES--1) To evaluate the morphological changes of the morphometry and compare them to the intestinal mucosa of children bearing Asymptomatic Environmental Enteropathy (AEE). 2) To compare the number of intra-epithelial lymphocytes (IEL) found in acute and/or persistent diarrhea by EPEC to those ones found in the other two groups. MATERIAL AND METHODS--Thirty (30) specimens of small intestinal mucosa obtained from children having acute and/or persistent diarrhea by EPEC were analysed and then compared to the specimens of the small intestinal biopsy of sixteen (16) patients bearing AEE. The following measurements were performed: RESULTS-- [table: see text] CONCLUSIONS--The villous changes were more remarkable in EPEC infection but the crypt hypertrophy was significantly higher in patients with AEE. This fact is probably due to repeated damages caused by the environmental problems. The use of linear morphometry has been a relevant technique which allows to evaluate the possible small intestinal morphological changes more accurately than the subjective criteria. In this way, the application of this technique enables the comparative approach of determined values under statistical bases.