The in vitro anticoagulant and fibrinolytic activities of crude extracts from insects were evaluated in order to find effective therapeutic drugs for the treatment of myocardial and cerebral thrombosis. We prepared three types of extracts (water, methanol and ethylacetate) from 28 insects for use as raw materials for the activity assays. The fibrinolytic activity was tested using the fibrin plate method and the activated partial thromboplastin time and thrombin time were measured for blood clotting activity. With regards to the fibrinolytic system, water extracts of six kinds of insects displayed a remarkable level of activity with a plasmin-like action. The water extracts of [Catharsius molossus, Eupolyphaga sinensis, Huechys sanguinea, Mantidis $oddot{o}theca$, Mimela splendens, and Polistes mandarinus (Vespae Nidus)] exhibited the activity. On the other hand, the methanol extracts did not display any fibrinolytic activity. In terms of the coagulation system, an aqueous extract of silkworm Tongchunghacho (Paecilomyces japonica), Oxya japonica japonica and Buthus martensi (Scorpion) increased the clotting time significantly longer (181 times) than the control. These results suggest that crude drugs from insects are useful sources for the development of new drugs for use in treatments involving blood coagulation and fibrinolysis.