Human immunodeficiency virus (HIV) which includes human retroviruses (LAV/HTLV-III), has been identified as the etiologic agent of AIDS1-3 One of the most significant aspects of HIV infection in humans is related to its probable origin. Serologic studies indicate that HIV may have been present in Africa since at least the mid-1970's4. In regard to the western hemisphere, little is known about the seroepidemiology of HIV infection. As part of national policies outlined by the Secretary of Health to monitor AIDS in Venezuela, we designed a seroepidemiological protocol to assess prospectively the characteristics of HIV infection in Venezuela.