Levels of alpha 2PI-plasmin complex and tissue-type plasminogen activator (t-PA) in plasma were determined in 10 cases of acute promyelocytic leukemia (APL) with marked coagulopathy and in 10 cases of hematological malignancies with DIC to investigate relevance to fibrinolysis. In the both groups, levels of alpha 2PI-plasmin complex increased and were inversely proportional to levels of fibrinogen and alpha 2PI. Levels of t-PA in plasma increased moderately in the majority of the both groups. Serial observation of the concentrations of t-PA with corresponding changes in the levels of fibrinogen, alpha 2PI, alpha 2PI-plasmin complex and FDP could not demonstrate any significant relationship between levels of t-PA and the other parameters. From these results, it is unlikely that levels of t-PA in plasma directly influence on the degree of consumption of alpha 2PI or of formation of alpha 2PI-plasmin complex in most cases of DIC.