As of July 1991, 10 years after the onset of this modern pandemia, it is estimated that greater than 1 million persons worldwide have AIDS, 10 million people are HIV infected and by the end of the millenium, there will be 40 to 50 million persons infected. In the United States, 120,000 persons already have died of AIDS and 200,000 currently are infected. It has been calculated that by the year 2000, primary CNS lymphoma will be more common than meningiomas. Clearly, AIDS-related complications involving the CNS and manifested by behavioral and neurologic manifestations will remain one of the most common problems for physicians worldwide for years to come.