Older patients are more susceptible to severe Epstein-Barr virus (EBV)-related infectious mononucleosis (IM). This condition may increase in industrialized countries where primary EBV infection occurs later in life. Between 1990 and 2004, 38 patients were admitted to our department with EBV-related IM. Two patients died. The annual incidence increased significantly (r = 0.623; P = 0.013).