Eleven patients with vascular ectasias of the colon and associated gastrointestinal hemorrhage were evaluated. All had the clinical features associated with aortic stenosis. In two patients, the configuration of the pulse wave in the mesenteric vessel was studied. In both, the abnormal peripheral pulse wave pattern associated with aortic stenosis was also transmitted to the ileocolic artery, where it differed quite clearly from the pattern in control patients. In a parallel study, the computer records of 3,623 patients with aortic or mitral stenosis admitted to the Mount Sinai Hospital over a 10 year period were reviewed for the presence of cryptogenic gastrointestinal hemorrhage. Twenty-one of 1,811 patients with aortic stenosis but only 1 of 1,812 patients with mitral stenosis had concomitant gastrointestinal hemorrhage (chi-square = 18, p less than 0.001). These data suggest that the cause of colonic vascular ectasias should be attributed to pathologic abnormalities of the arterial inflow pulse wave, rather than to chronic intermittent submucosal venous outflow obstruction.