The aim of this study was to determine the effects of pentoxifylline (Ptx) in reperfusion injury of the small bowel as a leukocyte stabilizer, free radical scavenger, and microcirculatory regulator. Ninety-six male Sprague-Dawley rats were used to determine the biochemical, histopathologic and blood flow changes of the reperfused small intestines after 30 minutes of a warm ischemic insult. Animals were divided into six groups: Sham (S), sham plus Ptx (SP), ischemia (I), ischemia plus Ptx (IF), reperfusion (R), and reperfusion plus Ptx (RP). Pentoxifylline was administered intraperitoneally at a dose of 50 mg/kg 15 minutes before ischemia. The superior mesenteric artery (SMA) was occluded distal to the right colic artery and collateral arcades were ligated as described by Megison. Sixty of the 96 rats (0 = 10) were used to determine histopathologic changes, malondialdehyde (MDA), and myeloperoxidase (MPG) levels in tissue. Mucosal lesions were graded on a scale from 0 to 5 as described by Chiu, MDA and MPO levels of the intestinal mucosa were assayed to reflect the free radical formation and neutrophil sequestration, respectively. Thirty-six rats (n = 6) were used to measure blood flow changes of the intestine using Xe-133 clearance technique. All data were presented as the mean values plus or minus the standart error of the means (means +/- sem). Although in the R group, mucosal injury score, blood flow, MPG, and MDA levels were higher significantly from the other groups (P < .05), in the RP group blood flow, MPG, and MDA levels were significantly decreased to the basal values (P < .05). Mucosal injury score of the RP group were lower than the reperfusion group but higher than the normal (P < .05). The authors conclude that pentoxifylline pretreatment before reperfusion stabilizes blood flow, decreases MPO and MDA levels to the normal, and attenuates but not completely prevents mucosal damage. Copyright (C) 1997 by W.B. Saunders Company.