A patient had a five-year history of sleep disturbance that culminated in a confusional illness with convulsions from which he made a partial recovery. On three separate occasions, the same ameba (Hartmannella rhysodes) was seen in and cultured from the patient's CSF. There was a rising serum titer of immobilizing antibody against the isolated strain of the ameba. The diagnosis of chronic amebic meningoencephalitis was considered in this patient.