The purpose of this study was to determine the effect of dietary ${gamma}$-linolenic acid on plasma lipid metabolism and anti thrombotic activity in male Sprague Dwaley Strain rats. Rats weighing an average of $100{sim}120g$ were fed a experimental diets containing 5% lard (saturated fatty acids), corn oil(linoleic acid), evening promise oil(EPO, 9% ${gamma}$-linolenic acid) or borage oil(BO, 24% ${gamma}$-linolenic acid) for 3Odays, respectively. Though there were no significant difference in the food intake among the groups, the body weight gain of the BO group was significantly lower than that of other group. The spleen weight of the lard group was significantly lower than that of other group. The bleeding time of the BO group was significantly longer than that of other group. The blood clotting time was significantly tended to long in EPO and BO groups compared with lard group. The plasma triacylglyceride and total cholesterol concentration were high in order of lard, com oil, EPO and BO, groups and there were significant differences among the groups. The plasma HDL-C concentrations were high in order of BO, EPO, com oil and lard groups and there were significant differences among the groups. The plasma LDL-C concentrations were significantly the highest in lard group, but the lowest in BO group. These data indicate that ${gamma}$-linolenic acid has a antithrombotic activity, and decrease the plasma triacylglyceride, total cholesterol and LDL-C concentrations in rats.