In 1982, an ethnographic pilot study of homeless youth was conducted in San Francisco, Los Angeles, and Seattle. Structured and unstructured interviews were completed with a sample of 250 males and females between 15 and 19 years of age in both natural and clinical settings. The interviews and participant observations of the street scene occurred from 1982 to 1984. In 1986, a small pilot study was developed to assess HIV infection among teenagers. The study was conducted over a 4-month period and included both HIV testing and behavioral interviews. Aware of demographic similarities between San Francisco and Rio de Janeiro (Brazil), cross-cultural comparative research was initiated in 1988 to study street youth and AIDS. In the U.S. studies, it was evident that personal and immediate survival needs dominated the lives of street youth. Adaptation and survival strategies of street youth in the western United States and Rio de Janeiro were similar in nature and often identical to those of the estimated 100 million street youth worldwide. Social inequalities and family disruptions are common in all countries. Further, a critical relationship exists between adaptation and survival strategies and the AIDS pandemic. The impact of this pandemic on street youth can be mitigated only by immediate and comprehensive preventive actions at both national and international levels. 14 references