Neurological manifestations of HIV infection are recognised at different phases of the evolution of the disease. During the late stages opportunistic neuro-meningeal infections and tumors develop as a result of the immuno-suppression. There exist, however, various manifestations which evolve independently of the immune state, and seem to be directly related to the virus itself. One can distinguish central neuro-meningeal syndromes and peripheral syndromes at the onset, or at later stages. Their prognostic implications are uncertain, but often severe, for example in the case of the subacute dementias which, in this setting, may lead to death in several months. There are also other manifestations which may be self limited or slowly evolving in the central and peripheral nervous systems. The neuropathological changes are known for the dementias as mentioned above, though the characteristics lesions due to HIV infection per se remain controversial. The presence of the virus in the nervous system has been established by in situ hybridization techniques, immunohistochemistry and culture. Studies on CSF have also allowed virological (cultures) and immunological studies to be carried out. The physiopathological mechanisms for the apparent neurological effects of this virus remain hypothetical. A better understanding of these mechanisms should lead to a rationalisation of therapeutic strategies, in a disorder which would seem to be an early and persisting viral infection of the nervous system.