Normal small intestinal folds are less than 2mm in thickness and criss-cross in appearance. Many diseases of the small interstine produce an abnormality in mucosal folds, namely thickening and parallel (perpendiulcer to the bowel lumen) arrangement of folds, nodularity, destruction, and ulcer. Diseases causing submucosal edema produce regular smooth thickening whereas diseases producing submucosal hemorrhage produce regular spiky thickening. Inflammatory bowel diseases and lymphoma produce irregular (in width, or distorted or 'bent at peculiar angles to the bowel lumen) thickening nodularity of the mucosa. Severe inflammatory processes as well as malignant tumors produce mucosal destruction and ulcer. Proposed here is an approach to narrow the category of disease processes based on mucosal fold abnormality. This approach with sufficient clinical history is invaluable in the interpretation of small bowel series.