This paper provides an exploratory analysis, using a qualitative approach, to perceptions by injecting drug users (IDUs) on: (a) risks associated with injecting practices; (b) risks of HIV/AIDS; and (c) prevention of HIV/AIDS. The study was conducted in five harm reduction programs in Brazil (the AjUDE-Brasil Project). Forty semi-structured interviews were carried out. The study focuses on the concept of “risk”. IDUs were mainly concerned over becoming ill and exposure to overdose and violence. IDUs dealt with individual problems in very specific ways in order to minimize them. They admitted that they were well informed about HIV/AIDS but lacked knowledge on reinfection and other bloodborne diseases. IDUs intended to follow guidelines established by health campaigns, but their addiction usually made it difficult. IDUs also suggested alternative harm reduction strategies and displayed a peculiar reading of concepts concerning sharing their injecting paraphernalia.