The portal blood flow of a 70-yr-old man with suspected massive mesenteric infarction was measured using duplex scanning. The main portal flow was 109 ml/min, while cardiac output was 4.2 L/min. Laparotomy revealed a massive mesenteric infarction from proximal jejunum to rectum. Duplex scanning may be a useful method for studying the course of mesenteric infarction.