Infectious mononucleosis(IM) Is an acute self-limiting lymphoproliferative disorder associated with infection by the Epstein-Barr Virus(EBV), with the characteristic triad of fever, sore throat, and cervical or generalized lymphadenopathy. And also there are atypical lymphocytes in the peripheral blood. Cytological findings of IM lymphadenitis are characterized by a florid immunoblastic and atypical lymphoid cell proliferation. However, the small number of cases were studied by fineneedle aspiration cytology(FNAC) even though there was a complexity of lymph node pathology. It is important to recognize the reactive pattern of IM that would initiate EBV study and to avoid unnecessary biopsy We studied findings of lymph node FNAC from 4 patients with EBV infection confirmed by EBV-specific serologic studios. All of the cases were positive for viral capsid antigen(VCA) and one case was positive for anti-EBV nuclear antigen(EBNA). Cytologically, all of the cases exhibited high cellularity and atypia with great numbers of large immunoblastic lymphocytes.