A 76-year-old woman was found to have acute aseptic meningoencephalitis with meningial irritation, disturbance of consciousness, elevation of cell counts in cerebrospinal fluid, and swelling of a right temporal-lobe lesion on a CT scan of the head. Muscle weakness in the lower extremities and urinary dysfunction developed and progressed gradually. The protein content of cerebrospinal fluid was high, and the distal latencies of F waves were prolonged, which suggested that the inflammation extended to the nerve roots. Sjögren's syndrome was diagnosed on the basis of atrophy of the labial salivary glands; invasions of lymphocytes and plasma cells to the intercellular space; and elevation of the titers of serum antinuclear antibody, anti-SS-A antibody, and anti-SS-B antibody. The patient had no xerosis. Aseptic meningoencephalitis was the first manifestation of Sjögren's syndrome. In recent years, several cases in which Sjögren's syndrome was associated with aseptic meningitis have been reported. However, we know of no previous report of such a case in a patient of this age. Aseptic meningoencephalitis can be the first manifestation of Sjögren's syndrome.