Aim:To determine whether mycophenolate mofetil(MMF)has beneficial effectson refractory idiopathic thrombocytopenic purpura(ITP)and the correspondingcellular mechanism.Methods:Twenty refractory ITP patients resistant to corti-costeroid and/or splenectomy and chemical therapy were given MMF 1.5-2.0g/dorally for a 2 to 4-month period.Serum immunoglobulin was detected by ratenephelometry.Platelet-associated antibodies(PAIgG)were assayed by enzyme-linked immunosorbant assay.The immunophenotypic analysis was performed ona flow cytometer and cell apoptosis was detected with transferase mediated dUTPbiotin nick end labeling(TUNEL)method.Results:Sixteen of the 20(80%)pa-tients had responses to MMF treatment;9(45%) achieved a complete response,4(20%)achieved a partial response,and 3(15%)achieved a minor response.Thetherapeutic effects were found to be better in male patients than female patients.The number of CD3~+ peripheral blood cells(PBCs)and CD4~+ PBCs increased andthe number of CD8~+ PBCs decreased.The plasma level of IgG,IgM,IgA andplatelet associated IgG(PAIgG)decreased in 86% of the patients.TUNEL assayshowed that mycophenolate acid(MPA)0.1 mmol/L induced apoptosis of periph-eral blood mononuclear cells isolated from refractory ITP patients.The apoptosisrate was increased in male patients after treatment with MPA,but was unchangedin female patients.Conclusion:Therapy for a period of 8 to 16 weeks with median-dose of MMF was valuable for the treatment of refractory ITP.