Eleven patients with intestinal vascular malformations (VMs), all diagnosed by angiography, are presented. Two of the VMs were incidental findings in patients treated for other problems; the other nine patients all presented with gastrointestinal hemorrhage, and all had resection of the portion of intestine containing the VM. None has rebled. The specimens from these nine patients revealed a variety of histological findings. One VM was the vasculature of small bowel leiomyoma. Three other specimens contained obvious VMs without associated findings, and one specimen contained no identifiable pathology. In the remaining four specimens, a variety of inflammatory conditions were found on histological study, including one case of Crohn's disease and another of ischemic colitis. In only one of these specimens did we identify the VM. None of these last four cases conforms to the degenerative lesions described by Boley and his colleagues. Therefore, we propose a fourth type of VM that is associated with or perhaps secondary to another disease of the intestine. We precisely localized one VM in the duodenum during operation with the Doppler ultrasonic flow detector, thus enabling us to limit the extent of the resection. We also propose the use of this technique for pinpointing the area where sections should be made for histological study.