Epstein Barr virus (EBV) is the causative agent of Infectious mononucleosis (Glandular fever), Burkitt’s lymphoma and Nasopharyngeal carcinoma. Symptoms of Infectious mononucleosis are fever, sore throat and swollen lymph glands. It may involve spleen or liver also. EBV associated central nervous system (CNS) disease is most commonly associated with Primary CNS Lymphoma in patients with AIDS. CNS infection may also be detected in immunocompetent patients. A prospective and diagnostic marker for the development of post-transplant lymphoproliferative disorders (PTLD), especially in Epstein-Barr virus (EBV)-seronegative organ transplant recipients who receive anti-lymphocyte globulin for induction immunosuppression and OKT-3 treatment for early rejection.