Changes in arterial and hepatic venous blood ketone bodies were investigated following transcatheter hepatic artery embolization (THAE) in patients with hepatocellular carcinoma. Acetoacetaie/ β-hydroxybuty-rate ration (ketone body ratio) in arterial blood was positively correlated with those of hepatic venous blood (r = 0.960, p < 0.001), which reflects the mitochondrial redox potential in the embolized lobe. Nine cirrhotic patients were classified into three groups according to the changes in arterial blood ketone body ratio following THAE: Type A without decrease to below 0.7; Type B with a transient decrease to below 0.7, followed by its restoration within 5 hours; and Type C with decrease to below 0.7 without recovery within 5 hours. There were no serious complications in Type A and B patients. By contrast, severe sepsis and hepatic failure developed in Type C patients, possibly due to the extended embolization of both lobes. It is suggests that THAE can be successfully performed even in severely cirrhotic patients, as long as the embolized area is restricted to one lobe. In addition, changes in arterial blood ketone body ratios can give early information about the likely consequences of the THAE procedure just performed.