To find out the incidence and clinical presentation of parvovirus B19 meningoencephalitis, we tested samples of cerebrospinal fluid from 162 patients (one from each patient) with undiagnosed meningoencephalitis, who presented between March, 1997, and March, 1998 (an outbreak period) using nested PCR for B19 genes. Seven patients were positive; an incidence of 4.3%. Five additional cases of meningoencephalitis were detected from other years. Three patients with underlying disorders (haemophagocytic lymphohistiocytosis, Cockayne's syndrome, and Turner's syndrome) died. Neurological sequelae were observed in three surviving patients, all of whom had had striking abnormalities detected on brain scans done during the acute phase.