1. Inclusion of raw faba bean (Vicia faba L., minor) in the diet of growing chickens was shown to affect the performance of the birds and to produce a significant increase in the relative weight of the pancreas. This was attributable to dietary trypsin inhibitors. 2. Trypsin inhibitors also produced degenerative changes in pancreatic acinar cells. These were observed by light and electron microscopy. 3. Progressive cytopathological changes were observed in the intestinal tract. The duodenum, jejunum and ileum were altered, with extensive erosion, shortening and atrophy of microvilli. 4. The results endorsed previous findings obtained using different legume seed lines (Phaseolus spp). Faba bean produced similar local reactions in the pancreas and the intestine. This may be caused by the presence of lectins in the seeds.