The triad of gastric mucosal ischemia and lumenal acid and bile is known to be ulcerogenic. However, the explanation for progressive mucosal injury after resuscitation from hemorrhagic shock is not known, because ischemia does not persist. To test the hypothesis that persistent pathophysiologic arteriovenous shunting is the cause of progressive mucosal injury after shock, we studied in vivo canine gastric mucosal oxygenation and transmembrane potential difference during and after one hour of hemorrhagic shock with and without topical acid (160 mM HCl) and taurocholate (1 mM) in the mucosal bathing solution. Although systemic blood pressure and total gastric blood flow returned to normal after shock in all groups, only the group with topical acid and taurocholate developed mucosal erosions and had persistent hypoxia and inhibition of potential difference in surface epithelial cells. We conclude that pathophysiologic arteriovenous shunting persists in the superficial part of the gastric mucosa after shock. It is tempting to speculate that shunting may replace ischemia in the ulcerogenic triad during the postresuscitation phase of injury.