It has been known that nasopharyngeal carcinoma was easy to invade into surrounding tissues and metastasize to distant organs, when compared with the other cancer of head and neck. On the other hand, it has been known that EB virus was closely related to the development of nasopharyngeal carcinoma. Furthermore, it has been clarified that transformed cells by EB virus had a large amount of plasminogen activator (PA). From the above-mentioned background, coagulation-fibrinolysis systems in patients with NPC and PA activity of tissue extract were evaluated in relation to mechanism of invasiveness and metastasis. 55 cases of NPC and 27 cases of other cancer in the head and neck seen, at the Department of Otorhinolaryngology in Guanxi University and affiliated hospitals in the south of China, were studied on coagulation-fibrinolysis system in these patients and proteases in tissue extract of NPC. In coagulation-fibrinolysis system, fibrinogen level, α2-pl asmin inhibitor (α2-PI) activity and antithrombin III (AT-III) activity were estimated in patients with NPC and other cancer. In estimation of protease activity of tissue extract with NPC, azocaseinolytic acivity was determined as activity of plasminogen activator. Compared with control group (group of healthy adult), fibrinogen level and FDP content in patients with NPC were significantly increased. However, α2-PI activity and AT-III activity were not statistically different from those with healthy group. Specific activity of PA in tissue extract with NPC decreased at stage IV compared with that at stage III, but statistical difference was not observed. From these results, it was suggested that non plasminic fibrinolysis occurred in the circulating blood of patients with NPC, and PA in tissue extract with NPC was consumed at stage IV. At present time, platelet function was in progress studying in circulating blood of patients with NPC from the aspect of control of metastasis and invasiveness.