Conclusions: Duodenal villous atrophy is highly prevalent in renal transplant recipients irrespective of age, sex, and posttransplant duration. We found tropical sprue, giardiasis, immunoproliferative small intestinal disease, and celiac disease to be important causes of duodenal villous atrophy. Therefore, duodenal biopsy is recommended in renal transplant recipients with persistent diarrhea.