Slow virus diseases are characterized by a long asymptomatic period, often months or years in duration, between the introduction of the infectious agent and the appearance of clinical illness. Two distinct groups cause serious degenerative diseases of the brain and spinal cord. The first to be identified are those caused by “unconventional agents,” kuru and Creutzfeldt-Jakob disease. The second category, “conventional virus diseases,” include SSPE (subacute sclerosing panencephalitis), PML (progressive multifocal leukoencephalopathy), progressive rubella encephalitis, and HIV encephalopathy. The universal focus on acquired immune deficiency syndrome (AIDS) has stimulated new research on slow viruses. The extreme neurological deficits, the chronic nature of these diseases, and the possible concern with infection control make patients with these diseases a challenge to nursing.