A retrospective study of 19 cerebrospinal fluid (CSF) specimens from 14 HIV-positive subjects with subacute encephalopathy, neuropathy, or unexplained peripheral myelopathy was done comparatively with plasma specimens collected on the same day and tested in the same run as the corresponding CSF specimen. A single patient had a high HIV RNA level in CSF as compared to plasma (CSF/plasma ratio > 10), which seemed correlated with the clinical course. Further studies are needed to confirm that a high CSF/plasma HIV RNA ratio is associated with greater symptom severity.