Objective To study in vivo effect of all trans retinoic acid (ATRA) or arsenic trioxide (As 2O 3) on the expression of tissue factor (TF) and the hemostatic disorders, a series of parameters were measured in bone marrow blasts and plasma from acute promyelocytic leukemia (APL) patients Methods The plasma variables were measured by ELISA or chromogenic study The TF transcription was assessed using reverse transcription polymerase chain reaction technique (RT PCR) Results The blast cell procoagulant activity (PCA), TF antigen of APL cell lysates, as well as the transcription of APL TF mRNA elevated at diagnosis, were reduced after ATRA or As 2O 3 therapy The plasma level of platelet α granular membrane protein 140, soluble fibrinomonomer complex, thrombomo~dulin, tissue plasminogen activator and D dimer significantly increased, fibrinogen, antigen level of protein C, plasminogen, α2 plasminogen inhibitor and plasminogen activator inhibitor decreased at diagnosis, were restored to normal after complete remission but protein C activity and protein S remained elevated in ATRA group Conclusions There existed activation of platelets and consumption of anticoagulants as well as activation of coagulation and fibrinolytic system before treatment Both ATRA and As 2O 3 therapy down regulated the expression of TF mRNA, decreased the PCA and TF level in APL cells, inhibited coagulation activation, secondary hyperfibrinolysis and recorrected other hemostatic abnormalities, thus greatly improved the bleeding symptom in early stage of the treatment Objective To study in vivo effect of all trans retinoic acid (ATRA) or arsenic trioxide (As 2O 3) on the expression of tissue factor (TF) and the hemostatic disorders, a series of parameters were measured in bone marrow blasts and plasma from acute Promyelocytic leukemia (APL) patients Methods The plasma variables were measured by ELISA or chromogenic study The TF transcription was assessed using reverse transcription polymerase chain reaction technique (RT PCR) Results The blast cell procoagulant activity (PCA), TF antigen of APL cell lysates, As well as the transcription of APL TF mRNA elevated at diagnosis, were reduced after ATRA or As 2O 3 therapy The plasma level of platelet α granular membrane protein 140, soluble fibrinomonomer complex, thrombomo~dulin, tissue plasminogen activator and D dimer significantly increased, Fibrinogen, antigen level of protein C, plasminogen, α2 plasminogen inhibitor and plasminogen activator inhibitor decreased at diagnosis, Were restored to normal after complete remission but protein C activity and protein S elevated elevated in ATRA group concludes there existed activation of platelets and consumption of anticoagulants as well as activation of coagulation and fibrinolytic system before treatment both ATRA and As 2O 3 therapy down regulated the The expression of TF mRNA, decreased the PCA and TF level in APL cells, inhibited coagulation activation, secondary hyperfibrinolysis and recorrected other hemostatic abnormalities, .cie significantly improved the bleeding symptoms in early stage of the treatment