A B S T R A C TThe effect of a faba bean diet on disaccharidase and dipeptidase activities in rat small intestine has been studied. Both maltase and sucrase activities significantly decreased in rats fed on the faba bean diet as compared with the controls. The inhibition seems to follow a non-competitive or mixed non-competitive pattern. On the other hand, legume-fed rats showed a slightly higher activity for intestinal glycyl-L-valine hydrolase. It has been suggested that the low nutritional value of diets containing Vicia faba, as a source of protein, was due to a reduction in both nutrient utilisation and intestinal enzymic activity, where polyphenolic compounds are possibly involved.