Abstract： AIM:To explore the possible role of Notch signaling in occurrence of acute promyelocytic leukemia(APL)through investigate the expression of Notch receptors, ligands and target gene in the bone marrow of patients with APL.METHODS:Semi-quantitative reverse transeriptase-polymerase chain reaction(RT-PCR)was used to investigate the expression of Notch1,Notch2,Notch3,Notch4,Delta-like-1,Delta-like-4,Jagged1,Hes1, Hes5 in the bone marrow of patients with APL,and the changes of expression after treatment.RESULTS:The expres-sions of Notch2, Jaggedl and Hesl were significantly lower after treatment, the expressions of the others have no significant difference. CONCLUSION:The changes of Notch2, Jagged1 and Hes1 expression after treatment are significant. The difference on the expression of Notch receptors and ligands may be important significance for the pathogenesis of APL.