Valine-depleted amino acid imbalance solution markedly inhibits tumor growth but causes fatty liver as a side effect. However, much remains unknown about the mechanism of the development of fatty liver. Valine-depleted amino acid imbalance solution containing various concentrations of calories was administered to tumor-bearing rats for four days by means of total parenteral nutritional methods to investigate the interaction of caloric intake and the development of fatty liver. Compared with the total parenteral nutrition control group the triglyceride content of the liver rose significantly in the group given valine-depleted amino acid imbalance solution with an increase in caloric intake. Plasma total protein and albumin significantly decreased. The very-low-density lipoprotein concentration in serum was also significantly lower than that in the control group. Valine-depleted amino acid imbalance caused hypoproteinemia, suggesting a fall in synthesis of apolipoproteins in the liver indispensable for lipid release. Along with the increase in the total caloric intake, triglyceride synthesis in the liver increased, resulting in augmentation of fatty content of the liver, probably because of the decreased lipid release.