Strong social support networks have been associated with positive outcomes for health and well-being throughout the life-cycle. This paper investigates the structural and functional nature of social support networks of 100 injecting drug users (IDUs) in Sydney and the implications for HIV/AIDS services. Using a modified ISEL respondents saw support in terms of its tangibility of people and support, in terms of an appraisal of having friends, and as a self-esteem measure. We found the majority of respondents ‘hung around’ with other IDUs, lived with other IDUs, and were satisfied with the support they received from their friends. Friends appeared to be a more important source of social support than biological families and if respondents were to become HIV infected they would be more open about their status with friends than family. Where family was involved in support it was likely to be provided by mothers and siblings who were also the family members who knew about the respondent's drug use. There was no relationship between numbers of supports and satisfaction of support, suggesting quality and quantity of support were independent. Non-social supports were conceptualized primarily in terms of medical services.