Nonspecific investigations resulting in treatment delays contribute to the 30 per cent mortality associated with acute mesenteric ischemia (AMI). As preliminary studies indicate that alpha-glutathione S-transferase (alpha-GST) is elevated in AMI we compare the ability of alpha-GST against conventional biochemical tests to predict AMI. There were 58 patients prospectively evaluated for AMI. Samples for alpha-GST (Biotrin International, Dublin, Ireland), lactate, pH, amylase, base excess, and white blood cell count (WBC) were evaluated. Intestinal ischemia was confirmed by colonoscopy, angiography, or laparotomy. Ischemia was present in 35 (60%) patients: small bowel (n = 14), colonic (n = 17), and global (n = 4). Four patients without autopsy were excluded. Alpha-GST was elevated in those with AMI [22.2 (7-126) ng/mL vs 2.2 (1-3) (P = 0.001)]. Alpha-GST was more accurate at predicting intestinal ischemia (74%) than conventional tests (47-69% accuracy). Accuracy was increased to 80 per cent by combination with lactate or WBC, which increased sensitivity to 97 to 100 per cent. Alpha-GST monitoring is a useful tool for the diagnosis of intestinal ischemia. A normal alpha-GST and WBC may exclude the presence of AMI.