ObjectiveTo improve the understanding of the diagnosis and therapy of chronic active Epstein-Barr virus (CAEBV) infection. MethodsData of 9 cases of CAEBV infection diagnosed between October 2008 and January 2013 were analyzed retrospectively,including clinical and auxiliary examination results,pathological data,especially EB virus (EBV) antibodies and DNA in peripheral blood mononuclear cells (PBMC) and infected tissue,and follow-up information. ResultsThe major manifestations of the 9 patients were fever,splenomegaly,hepatomegaly,lymphadenopathy,and others,including general fatigue,nausea,skin rash,jaundice,and so on.The abnormalities of auxiliary examination were as follows:anemia,leucopenia,neutropenia,thrombocytopenia,elevated LDH and HBDH levels,liver dysfunction and abnormal chest CT findings.EBV serologic tests revealed high IgA antibody levels against EB viral capsid antigen (VCA) in 6 patients,and 8 patients had positive IgG antibody levels against early D antigen (EAD).The mean load of EBV-DNA detected by real time polymerase chain reaction (PCR) in the PBMC was 3.07×105 copies/mL.Six of the nine patients presented a poor clinical course.One of them died of intracranial hemorrhage,one of them died of multiple organ failure,one of them died of EBV-associated hemophagocytic syndrome,and one of them died of severe pulmonary infection.Four patients developed lymphoma.One of them died of hepatic failure and one of them died of severe infection in the process of anti-tumor treatment. ConclusionThe clinical feature of CAEBV infection is varied.More attention should be paid to the disease because of its severe complications,poor prognosis and high mortality.