The paper addresses the socio-geographical spread of HIV/AIDS among injection drug users (IDUs) in Brazil, highlighting patterns and trends of the epidemic in different Brazilian regions. Data relative to the Southeast are reviewed and original analyses for the South are presented. The results indicate that the epidemic is diminishing in the Southeast, after a significant increase in the late 1980s, following major cocaine trafficking routes. On the other hand, the AIDS epidemic is far from leveling off in the South. In this region, IDUs have been pivotal in the dynamics of the epidemics. This explains, at least partially, the recent spread in the South, affecting a large number of women, most of them partners of IDUs, and their offspring, and contributing for a less significant decline of AIDS related deaths, when compared with other Brazilian regions.