The clinical features, the results of gastric secretory function tests, and the duodenojejunal morphology of six infants (aged 0.42-1.23 years) with anemia and melena considered to be due to latent cow's milk intolerance (LCMI) were compared with the findings in nine infants (aged 0.19-0.87 years) with cow's milk-induced malabsorption (CMI). The infants with LCMI had a short period of breast feeding, normal weight gain without symptoms of malabsorption, and no atopic history. The maximal acid secretion was decreased (p < 0.01) and the concentration of fasting serum gastrin raised (p < 0.01) compared with the controls. Gastric biopsy revealed epithelial degeneration in three and erosion in one out of four samples. The duodenojejunal biopsy revealed slight changes in two samples, the others being normal. The number of eosinophils was increased in four out of six biopsies. Although the number of intraepithelial lymphocytes was increased in LCMI the rise was not as significant as in children with CMI (p < 0.05). We conclude from our results that LCMI seems to be a seperate clinical entity. The determination of fasting serum gastrin, maximal gastric acid secretion and intraepithelial lymphocytes on duodenojejunal biopsy appear to be helpful in making the diagnosis.