This study assessed the effect of continuous infusion of prostacyclin on tissue blood flow throughout the GI tract to see whether small and large bowel flow was also affected. Twelve miniature swine were anesthetized, ventilated, and hemodynamically monitored. After stabilization each animal received either prostacyclin in buffer at 0.1 mcg/kg/minute for 3 hours or buffer alone (controls). Tissue blood flow was documented at baseline and at 1, 2, and 3 hours of prostacyclin infusion by injection of radiolabeled spheres. Prostacyclin infusion did not significantly affect mean arterial pressure, heart rate, or cardiac index compared to controls. At 3 hours tissue blood flow was significantly increased in the gastric mucosa (↑ 225%), small bowel (↑ 110%), cecum (↑ 260%), and transverse colon (↑ 160%) compared to controls. Prostacyclin may be an effective agent for prevention of ischemia in all areas of the GI tract prone to stress ulceration.