Social workers are often on the front lines of the HIV/AIDS epidemic delivering prevention education and interventions, offering or linking individuals to HIV testing, and working to improve treatment access, retention, and adherence, especially among vulnerable populations. Individuals with substance use disorders face additional challenges to reducing sexual and drug risk behaviors, as well as barriers to testing, treatment, and antiretroviral therapy adherence. This article presents current data on HIV transmission and research evidence on prevention and intervention with substance abusers and highlights how individual social workers can take advantage of this knowledge in practice and through adoption and implementation within organizations.