Two patients diagnosed as having acute promyelocytic leukemia (APL) and disseminated intravascular coagulation (DIC) were closely followed by serial fibrinolysis and coagulation studies from the day of admission until completion of the first course of chemotherapy. One patient was treated with intravenous heparin and Trasylol (Bayer AG, West Germany) and the other received heparin therapy without Trasylol. In Patient 1, hyperfibrinolytic activity, not observed during the administration of Trasylol, developed with its discontinuance. In Patient 2, hyperfibrinolysis was observed coincidentally with a decrease in APL cells due to chemotherapy. These results indicate that hyperfibrinolysis in APL is not associated with DIC.