The digestion of protein by rats infested with the intestinal nematode N ippostrongylus muris (Yokogawa, 1920) was measured directly by feeding by stomach tube egg albumin labelled with radioiodine. One hour later nearly 70 per cent. was recovered from the gastro�intestinal tract of infested rats, but only 50 per cent. from that of normal rats. This difference was due largely to a depression of digestion in the small intestine, although absorption was also slightly reduced. Gastric digestion was not affected, nor was there any difference between the rates of gastric emptying by normal and infested rats.