In this study, effect of prostacyclin on ischemia reperfusion injury, that was performed in the jejunum of horse was investigated. In 12 horses total arterio venous occlusion was performed in 25 cm of a jejunal segment. In all cases, I h reperfusion was performed after 2 h of no flow ischemia. Twelve horses were assigned into two equal groups, one as a control (1) group and the other as a prostacyclin (2) group. In the 2 nd group, I Lisotonic NaCl solution including diluated PGI(2) was administrated into the jugular vein for five minutes before the occlusion at a rate of 5 ng/kg/min and increased to 25 ng/kg/min during the occlusion and decreased to 5 ng/kg/min for first five minutes of the reperfusion and continued during the remaining reperfusion period. In all cases tissue samples and photographs of the jejunum were obtained 15 min before the occlusion, 10 minutes before the reperfusion and at the end of reperfusion for TEM and gross pathology. Blood samples were collected from the facial artery in order to measure TNF alpha and IL-6, 15 min before the occlusion, 10 min before the reperfusion and at the end of reperfusion in all cases. In the control group, while the dark muddy brown appearance of Ischemic Strangulative Obstructioned (ISO) segments were constant after the reperfusion; in the PGI(2) group moderately anemic appearance, that was caused via ischemia, was back to normal after the reperfusion. After the reperfusion, irregular microvilli and excesive mitochondrial cristalysis were observed in the control group; and short but regular microvilli and many mitocondria with cristae were observed in the PGI(2) group. During the experiment period, serum TNF alpha values were increasing in the control group and were decreasing in the PGI(2) group. IL-6 levels could not be detected in many cases. In conclusion, prostacyclin has been found useful to decrease the ischemia reperfusion injury of horse jejunum according to the results of TEM and macroscopic pathology and the level of TNF alpha.