We present a case of reactive angioendotheliomatosis (RAE) of the colon, featuring intravascular proliferation of endothelial cells with histologic resemblance to glomeruloid hemangioma. A 19-year-old Japanese male with an anal fistula was diagnosed endoscopically with Crohn's disease. Six months later, he was hospitalized for fever and abdominal pain. Emergency resection of ileocecum and splenic flexure of the colon was undertaken to control massive intestinal hemorrhage, and in all parts of the resected colon, foci of many small vessels with intravascular proliferation of endothelial cells were noted throughout the layers. Moreover, solid proliferation of endothelial cells was seen in the submucosa at the base of open ulcers. Two small granulomas, compatible with Crohn's disease, were also evident in the muscle layer of the terminal ileum. No other hemangiomas or hemangioma-like structures were observed with CT scans, and the vascular lesions were histologically diagnosed as RAE. The pathogenesis of this disorder is unknown, and most cases occur in skin with systemic disease. The present case might thus be a first case of RAE of the intestine without cutaneous involvement. Whether there is a relation with coexistent enteritis suggestive of Crohn's disease needs to be clarified.