A 26-year-old woman, who had been treated with prednisolone 30 mg/day for secondary Sjögren syndrome (SjS) with systemic lupus erythematosus (SLE), was complicated with aseptic meningoencephalitis (AME). Cerebrospinal fluid (CSF) cell counts were 26/3, total protein 126 mg/dl, glucose 41 mg/dl. The CSF, blood, nasopharyngeal swab were cultured for bacteria, mycobacteria, viruses and fungi, but no evidence for an infectious etiology was obtained in this patient. The pair sera study for viruses titer were performed, but no significant titer elevation was observed. Head magnetic resonance imaging showed remarkable atrophy of bilateral occipital lobe and dilatation of posterior horn of bilateral ventricles. The high 2-5AS enzyme activity in the CSF suggested indirectly that the cause of this meningoencephalitis was virus infection. In this case microbiological studies were negative, so central nervous system SLE and/or central nervous system SjS were not completely neglected.