Spinal and cortical SEP responses were recorded during tibial and median nerve stimulation in 58 HIV+ subjects (8 IV/C1, 24 IV/C2 & IV/A, 11 III and 15 II), all asymptomatic from a neurological point of view. The electrophysiological features were compared with clinical assessment and serum HIV markers for purposes of prognosis and therapy. In group IV we observed a slowing of conduction along the afferent pathway in the spinal tracts and afferent ways to the cortex. The major part of the delay occurred in the mid and lower medullary tract. These results agree with neuropathological finding from post-mortem examination in AIDS pts.