This study was investigated to find the effects of petroleum ether extract (Lipophilic fraction) from Korean red ginseng on platelet aggregation and thrombin time of the plasma in two groups of the experimental rats. One group of rats were fed with 15% corn oil (15%kg-diet) containing a number of 18 : 2 (linoleic acid) or 15% beef-tallow (15%/kg-diet) containing saturated fatty acids for 3 weeks, and were followed by feeding the petroleum ether extract (25 mg/kg-diet) for 3 weeks. The other group of rats (control group) were fed with 15% corn oil or 15% beef-tallow for 6 weeks. The platelet aggregation induced by thrombin and collagen was significantly inhibited and the thrombin time was prolonged in the 15% corn oil plus petroleum ether extract administrated group than in the 15% corn oil administrated group. And the same results were shown in the 15% beef-tallow plus petroleum ether extract administrated group. These results suggest that the petroleum ether extract from Korean red ginseng may have the beneficial effects on the inhibition of the platelet aggregation and the inhibition of blood coagulation induced by dietary fats.