This article documents the clinical course of nine patients diagnosed as having malignant histiocytosis of the intestine (MHI). Five patients had a history of gluten-sensitive enteropathy. This tumor commonly affects the small bowel in a widespread, patchy fashion causing ulceration, stricture formation, and perforation. Metastases to mesenteric nodes, liver, and the bone marrow were common. Although the diagnosis of MHI was often made at laparotomy, surgical resection, even when extensive, was not curative in any case. All nine patients were treated with a variety of chemotherapeutic regimes. This tumor proved chemosensitive, although response was usually brief and difficult to accurately evaluate. Chemotherapy was poorly tolerated because these patients were malnourished. In two cases small bowel perforation occurred, and in one gastrointestinal bleeding occurred after chemotherapy. Eight patients have died of disease from 0 to 16 months after the diagnosis was made, and a single patient is apparently cured 5+ years after completing chemotherapy. Malignant histiocytosis of the intestine has a characteristic clinical course. It is hoped that increased clinical awareness and early diagnosis will improve the outcome.