A 3-year-old girl of Navajo heritage had intractable diarrhea beginning at 4 days of age and resulting in long-term hyperalimentation. Investigation before multivisceral transplantation included biopsies of the rectum, stomach, duodenum, and liver. The diagnosis of microvillus inclusion disease was established by documentation of microvillus inclusions in duodenal epithelial cells. A trial of somatostatin therapy was ineffective in controlling the diarrhea. Subsequently, a multivisceral organ transplant provided a unique opportunity to establish the gastrointestinal extent of involvement of this disease. Ultrastructural microvillus inclusions were identified in the duodenum, jejunum, ileum, and colon, but not in the gallbladder. A few inclusions also were documented in gastric antral epithelial cells. Alkaline phosphatase stains performed on paraffin-embedded material showed a few inclusions in the antrum of the stomach and many inclusions throughout the small intestine, primarily in surface epithelial cells but also in upper crypt cells.