We examined fibrinolytic substances in homogenate of leukemic cells, normal granulocyte or mononuclear cells fraction. Plasminogen activators (PA) were significantly low in normal cells, but they were slightly increased in lymphoblastic leukemia cells and markedly increased in myeloblastic leukemia cells. In almost leukemic cells homogenate, the antigen ratio of tissue type PA (t-PA)/urokinase type PA (u-PA) was about 2.0. In especially AMMoL and AMoL, PA activity had discrepancy between euglobulin lysis time and amidolytic assay using chromogenic substrate. As PA inhibitor (PAI)-II was markedly increased in them. PAI might effect the PA assay. PA activity of leukemic cells homogenate was similar to that without t-PA stimulator and leukemic cells homogenate significantly stimulated t-PA. As both PA activity and antigen were statistically increased in leukemic cells homogenate of patient with disseminated intravascular coagulation (DIC), PA and PA stimulator in leukemic cell might play an important role in hypofibrinogenemia or DIC.