A 19-year-old man developed recurrent aseptic meningitis (Mollaret's meningitis) during the course of acute Epstein-Barr virus infectious mononucleosis. Serum contained heterophil antibody and Epstein-Barr virus-specific antibodies characteristic of acute infection. Seven brief episodes of aseptic meningitis were documented over the following one-year period, in each case with a polymorphonuclear pleocytosis in the cerebrospinal fluid. Acute infection with Epstein-Barr virus, or subsequent reactivation of virus, may account for some cases of Mollaret's meningitis.