Dietary lectins of gluten origin have been suggested to play an important role in the mechanisms leading to the characteristic morphology of the intestine found in patients with celiac disease. To further explore this issue we have used Wheat Germ Agglutinin (WGA) or Concanavalin A (Con A) to challenge rat small intestine and study the ultrastructural changes of such a treatment. Both lectins affected the enterocytes at the base of the villi more than those at the top. The morphological findings included disarrange-ment of the cytoskeleton, increased endocytosis and shortening of the microvilli. The interrelationship between the observed changes, and their relevance for similar morphological alterations found in patients with celiac disease are discussed. In conclusion, the morphological findings in our rat model resemble early changes in patients with celiac disease, thus supporting the idea that lectins or lectin-like substances are involved in the pathogenesis of this disease.