We analysed the characteristics of 372 Epstein-Barr virus (EBV) infected patients visiting our hospital from 1981 to 1995 classifying the phase I (from 1981 to 1988), the phase II (from 1989 to 1991) and the phase III (from 1992 to 1995). The incidence of infectious mononucleosis (IM) as EBV primary infection increased especially in the patients over 30 years old in the phase II and III. Immunological data on EBV specific antibodies showed twice positivity for anti EBV VCA-Igm antibody and the patients with anti-EBNA antibody decreased in the phase II and III. It is indicative of early diagnosis on primary EBV infection. EBV also causes atypical diseases, non-IM in this report, including hematological or neurological disorders. In hematological ones, one of 4 cases with virus associated hemophagocytic syndrome (VAHS) took fatal courses in the phase I, others had recovered by early diagnosis and adequate therapies (pulse therapy of steroids, exchange transfusion etc.). We indicated here the increased number and advanced age of patients with IM and improvement of the early diagnosis in recent 6 years compared with the previous 8 years.