Objective : This experimental study was carried out to investigate the effects of Persicae Semen(PS) and Caesalpiniae Lignum(CL) on the intravascular coagulation which is considered as thrombosis. Methods : Rats were pretreated orally with PS and CL extracts(PS: 8.45mg/100g, CL: 4.4mg/100g), and 1 hour later, to induce thrombosis, were given an endotoxin(0.01mg/100g) injection into the caudal vein. After 4hours we collected blood by cardiac puncture and measured the platelet count, the prothrombin time, the level of fibrinogen and the FDP(fibrinogen degradation product). Results : PS and CL supressed the decrease of the Platelet count and the prolongation of prothrombin time. In these factors, both groups showed significant effect. Both groups supressed the decrease of the fibrinogen level and the increase of the FDP level. But, only the PS group showed a significant effect on the fibrinogen level, and only the Cle CL group showed a significant effect on FDP level. Conclusions : PS had significant effects on the platelet count, the prothrombin time, and the FDP level. CL had significant effects on the platelet count, the prothrombin time, and the fibrinogen level. Therefore, PerSicae Semen and Caesalpiniae Lignum seem to be applicable to treating the diseases related to thrombosis.