This study was carried out to determine the effect of dietary ${gamma}$-linolenic acid on decreasing the plasma lipid levels and the thrombotic activity in rats. Sprague-Dawley male rats (B.W 120 g) were fed a experimental diet containing 5% lard (46.05% saturated fatty acids) , corn oil (51.36% linoleic acid) , evening primrose oil (EPO,72.80% linoleic acid and 9.16% ${gamma}$-linolenic acid) or borage oil (BO,40.29% linoleic acid and 24.25% ${gamma}$-liolenic acid) for 30 days. Although there were no significant differences in the food intake among the groups, the body weight gain of the BO group was significantly lower than that of the other groups. The bleeding time of the BO group was significantly longer than that of the other groups. There were significantly differences in the whole blood clotting time among the groups except for the EPO and corn oil groups, where the whole blood clotting time of the BO group was the highest among the groups, and that of the lard group was the lowest. The plasma triacyglyceride (TAG) , total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) concentrations were the lowest in the BO group, but highest in the lard group, and there were significant differences among the groups. The plasma HDL-C concentrations were in the following order: BO, EPO, corn oil and lard groups and there were significant differences among the groups. The excretions of fecal neutial steroids and acidic steroids of the BO group were the highest among the groups, and there were significant differences compared to the other groups. The results suggest that dietary EPO and BO containing ${gamma}$-linolenic acid has an antithrombotic activity, and inhibits the increasing of plasma TAG, TC and LDL-C concentrations compared to lard, which contains saturated fatty acids, or corn oil, which contains linoleic acid.