We have investigated the correlation between the arterial blood ketone body ratio (AKBR) and beta-hydroxybutyric acid (HBAC) in the course of a 75 g glucose tolerance test. The correlation was revealed to be represented by an equation of Y = A + BX [X = log(HBAC), Y = log(AKBR)] with high significance. This expression existed in both normal individuals and patients with liver, biliary tract or pancreas disease. The postoperative course was unsatisfactory because of liver dysfunction in cases whose value B was more than -0.6 in bisegmentectomy and more than -0.45 in uni- or subsegmentectomy. The coefficient B in the equation was suggested to contribute to the evaluation of hepatic functional reserve.