The present study was designed to examine the influence of aging on the gastric blood flow, a major mucosal protective mechanism against experimental gastric mucosal injury, basally and after treatment with acid, a known stimulant of gastric blood flow. Our data demonstrated that aging was associated with a significant decline in basal gastric blood flow (both mucosal and serosal). However, there were no significant differences in acid-induced increases in gastric blood flow between the young and aged animals. These findings suggest that aging is associated with selective and specific reductions in mucosal protective mechanisms that may predispose aged animals to gastric mucosal injury.