The effect of a single oral dose of malathion (1 g/kg body wt.) on the digestive and absorptive functions of the intestinal epithelium has been investigated in rats. The absorption of glucose and glycine was considerably reduced (35%) inpesticide fed animals compared to controls. The activities of brush border sucrase, lactase, alkaline phosphatase, Mg2+-ATPase and lactate dehydrogenase were also significantly depressed in malathion exposed rats, but there was no change in the leucine aminopeptidase levels under these conditions. Mucosal DNA, RNA and protein contents remained unaltered in pesticide toxicity. These results suggest that malathion toxicity induces functional derangements of the intestine.