Looking for an early laboratory parameter in diagnosis of acute bowel ischemia, we caused an acute ischemia of the rabbit bowel by clamping the superior mesenteric artery. The blood tests showed a significant increase of lactate during 80 min of ischemia. This lactate excess continued nearly 40 min after revascularization of the bowel, but disappeared nearly completely after 90 min. Neither the laparotomy without clamping the superior mesenteric artery, nor the experimental clamping of the a. femoralis communis led to a lactacidemia. The lactacidemia in our experiments is compared with clinical observations in acute bowel diseases and vascular surgery with clamping of the aorta. The reasons of the specific high lactate excess of bowel ischemia are discussed. The fast increase of the lactate following mesenteric vascular occlusion and the rapid normalisation of lactate after recovery demonstrate a sensitive method in the diagnosis and controlling the treatment of acute bowel diseases with an insufficient blood supply.