SummaryMorphometric studies and eosinophil counts in the lamina propria of the duodenal mucosa have been performed in patients with chronic nonspecific diarrhoea and with persistent diarrhoea due to a cow's milk allergy, using a semiautomatic image analysing system. The results have shown that the mean eosinophil count was significantly higher in both of these groups of patients compared with a control group (p < 0.001), and some of the patients with chronic nonspecific diarrhoea had partial villous flattening. These findings in patients with chronic nonspecific diarrhoea could be related to the pathogenesis of this disorder.