Brazil has been recognized for being the first developing country to provide universal AIDS treatment. Brazil also implemented a comprehensive prevention initiative. These efforts have been successful, with about half the number of HIV/AIDS cases forecast in 1992 developing by 2000. However, HIV/AIDS continues to spread, including among not-in-treatment drug users. Questions have been raised about gaps in existing prevention efforts. Based on qualitative research in 2006-2008 with street drug users in Rio de Janeiro (focus groups, N=24; a pile sort, N=108; open-ended interviews, N=34), this paper examines enduring gaps in HIV knowledge and prevailing risk patterns and proposes strategies for strengthening prevention.