In order to test whether or not overeating of a nutritionally adequate diet with reasonable fat content could result in significant fat accumulation in the liver, male Sprague-Dawley rats were provided with free access to either a nutritionally adequate liquid diet with 35 per cent of calories as fat or a regular diet (controls) for 3 months. After the feeding period, body weight, Lee index, and epididymal adipose tissue weight, were significantly greater in rats fed with the liquid diet than in the controls. Liver weight, hepatic triglyceride levels were also greater in the liquid diet group. Histologically, remarkable fatty infiltration was observed predominantly in periportal areas in rats fed with the liquid diet ad libitum for 3 months. Compared to a large body of the literature concerning diet-induced obesity in experimental animals, information on animal models of fatty liver by dietary manipulations is insufficient. The results of this study clearly indicate that the overeating of a nutritionally adequate diet with reasonable fat content could result in remarkable fat accumulation in the liver in rats.