Multiple endocrine neoplasia syndrome IIB is an inherited autosomal dominant disorder with variable penetrance. Multiple organ systems are involved with a characteristic triad of medullary thyroid carcinoma, pheochromocytoma, and alimentary tract ganglioneuromas. Most patients have characteristic facies with patulous lips and thickened tarsal plates of the eyelids. The entire gastrointestinal tract can be involved from tongue to anus. Tongue nodules are common. Altered intestinal motility, dilation, diverticula, and mucosal abnormality may be seen radiographically. Gastrointestinal symptoms are common, may be the presenting manifestation of the syndrome early in life, and allow the radiologist to suggest the proper diagnosis. Five patients are described. All had megacolon.