Chronic active Epstein-Barr virus infection(CAEBV) is a nonfamilial syndrome that shows a specific immunodeficiency for the Epstein-Barr virus(EBV). CAEBV is characterized by fever, lymphadenopathy, splenomegaly, hepatitis, interstitial pneumonitis, interstitial nephritis, and uveitis. Cardiovascular complications are rare in EBV infection. Patients with CAEBV show characteristically high titers of anti-viral capsid antigen(VCA) IgG antibody and anti-early antigen(EA) antibody, as well as relatively low titer of anti-EB nuclear antigen(EBNA) antibody. We experienced a case of CAEBV with giant coronary aneurysms, who was a 6-year-old boy. He had 5 episodes of high fever and cervical lymphadenopathy and hepatosplenomegaly. The 6 mm sized bilateral coronary aneurysms were detected by echocardiography at second admission. IgG antibodies to EBV was positive, whereas negative for IgM antibody. Antibodies to EA and EBNA were also positive. The EBV was detected in lymph node tissue by in situ hybridization, and in the peripheral blood and bone marrow by the PCR. Treatment has been done with ganciclovir and interferon (IFN)-alpa for 5 weeks. The EBV-PCR of peripheral blood was converted to negative from 12th day of treatment. At present he has followed well for two years without fever and enlargements of lymphnode, except large coronary aneurysm.