A variety of the central nervous system lesions may cause a diffuse encephalopathy in AIDS patients. Apart from viral encephalitides already described in part one, metabolic encephalopathies are a classical cause of diffuse brain dysfunction and are frequent at the terminal stage of the disease. Atypical forms of some infectious, vascular or tumoural processes which usually determine focal lesions, may cause diffuse encephalopathies. These forms are not exceptional in AIDS. The association in the same patient of lesions due to different agents is the rule. Whereas most of the neurological complications of AIDS occur late in the course of the disease, symptomatic, usually transient encephalopathies have been described in the early stages of HIV infection in rare cases. The authors conclude by proposing a management plan, since therapeutic advances have raised some hopes of improvement and even regression of some of these disorders in a few cases, so that physicians do not systematically give up when an AIDS patient presents with a diffuse encephalopathy.