Examination was made of the effects of edible oils containing medium-chain fatty acids (MCFA) on the body fat weight and blood lipid concentrations of rats fed a mixture of randomly interesterified rapeseed oil (87%) and medium-chain triacylglycerols (13%) (MLCT), and a physical mixture of rapeseed oil (87%) and medium-chain triacylglycerols (13%) (MIX). Wistar male rats were randomly divided into three groups and fed diets containing 7% rapeseed oil, MLCT and MIX for 6 weeks. Although the body fat weight and blood cholesterol concentration of rats fed MLCT and MIX diets were significantly lower than those of rapeseed oil diet, those of rats fed MLCT and MIX diets were not significantly different. The result suggests that the lowering effects of MCFA in the diet on body fat accumulation and blood cholesterol concentration in rats are similar to those caused by MLCT and MIX. It is of particular interest that the effective suppression of body fat accumulation in rats has been observed in the diet with a relatively small amount of MCFA (0.9% in experimental diet) when it is compared with the amounts of MLCT and MIX in diets.