Clinical studies show that patients with liver cirrhosis associated with portal hypertension have a high incidence of duodenal ulcer and duodenitis. However, little information is available concerning pathophysiological process of such duodenal diseases in liver cirrhosis. Hemodynamics of the duodenal mucosa was studied in cirrhotics with esophageal varices (68 cases) and in noncirrhotics with non-ulcer dyspepsia (37 cases) as well. In each group, hemoglobin concentration in the peripheral venous blood was measured, and mucosal hemodynamics was examined in 4 regions of the duodenum by endoscopic reflectance spectrophotometer. No significant intergroup difference was noted in the mean age or sex ratio. Hemoglobin concentration in the peripheral venous blood was significantly lower (p less than 0.01) in the cirrhotics. There were no significant intergroup differences in duodenal mucosal blood volume. However, the cirrhotics showed significantly lower oxygen saturation of hemoglobin in all regions of the duodenum (p less than 0.01). These results show that the cirrhotics with esophageal varices had relative increase in blood volume and decrease in oxygen saturation of hemoglobin in the duodenal mucosa. Such microcirculatory disturbances seem to predispose liver cirrhosis patients to duodenal injury.