About 30-40% of AIDS patients present CNS and/or PNS involvement, due to direct action of HIV virus or opportunistic infections. Nervous system involvement in the HIV correlated syndromes is not a rare occurrence; nevertheless no studies about prognosis of AIDS related syndromes have been published yet. We tested 38 HIV positive patients for the assessment of neurological complications by means of clinical and instrumental evaluations: multimodal evoked potentials, EMG/ENG studies, nerve and muscle biopsy. At the baseline evaluation, 26/38 patients had neurological complications: 14 of CNS, 9 of PNS, 3 of both CNS and PNS. At follow-up, 16/37 patients had developed AIDS and 10/16 patients with AIDS died. Of these 16 patients, 14 had clinical and neurophysiological alterations at the baseline evaluation. Our results suggest that the presence of clinical and/or neurophysiological nervous system involvement in patients with HIV-related syndromes constitutes a negative prognostic factor for developing AIDS.