Data came from the National AIDS Demonstration Research and AIDS Targeted Outreach Model projects funded by the National Institute on Drug Abuse. These projects recruited not-in-treatment IDUs and their sex partners between 1988 and 1992. This analysis used information from baseline interviews of 13,893 IDUs at 11 sites. Results suggested that, in comparison to United States-born IDUs, Mexican-born participants were at elevated risk for acquiring and transmitting HIV as a result of sharing needles with friends and running partners; sharing drug injection implements such as cookers, cotton, and rinse water; frequent injection in HIV-risky settings; the use of unsterilized needles; and relatively frequent trading of sex for drugs or money. Puerto Rican-born IDUs injected drugs relatively often and did so often in high-risk settings in which sterile injecting equipment and cleaning materials were often scarce. Foreign-born IDUs generally had lower levels of AIDS knowledge than those born in the United States. They most often cited television as the source of their most useful AIDS information and also regarded community outreach workers as significant sources of reliable information. Findings indicated a need for a comprehensive public health prevention initiative to limit the future spread of HIV; this effort should include group-specific, culturally appropriate behavioral interventions as well as an information campaign. Tables and 58 references (Author abstract modified)