This study examined drug use patterns, HIV/AIDS, and related outcomes among former Soviet Union (FSU) immigrants from Russia, Ukraine and the Caucasus mountain region in Israel who reported heroin use. A total of 253 FSU heroin users were interviewed from 2002 to 2007 as part of a large drug use surveillance study in Israel. Individuals were sampled at drug treatment facilities in an urban population center of the Negev region of Israel. Participants were assessed using the Addiction Severity Index, fifth edition. First, immigrants from Russia and Ukraine were compared; then, as a group, compared to those from the Caucasus region. Overall, ASI composite scores suggested comparable levels of addiction severity between the Russian and Ukrainian groups. However, Kavkaz immigrants are older, less likely to be employed, and have more severe scores on many of the drug use measures as compared to the other two nationalities. This study shows different drug use patterns exist among FSU immigrants. Such differences may be, in part, due to socioeconomic, geographic and other sociodemographic factors. Injection drug use, regardless of country/region of origin is a critical public health problem, especially given the link between injection drug use and infectious disease.