Hypoxanthine has been shown to be a sensitive and more specific measure of hypoxia than lactate in several body fluids other than peritoneal fluid. An experimental study was conducted to determine the value of peritoneal fluid hypoxanthine besides lactic acid levels in detecting vascular compromise of the intestine. Thirty male guinea pigs were divided in 3 groups each containing 10 animals. Groups comprised of sham operation control, simple intestinal obstruction and intestinal obstruction with vascular compromise. Lactic acid and hypoxanthine levels were determined in peritoneal lavage effluents. Peritoneal fluid lactic acid levels increased after 4 hours of intestinal obstruction with vascular compromise (p < 0.01) but not in simple intestinal obstruction and sham operation control groups. No detectable amount of hypoxanthine could be found in any of the fluid samples. It is concluded that unlike in other body fluids hypoxanthine is not present in peritoneal fluid and does not become evident after vascular compromise of the intestine.