The study used network analysis to identify forms and sources of social support associated with a medical services use among a medically underserved population living with HIV/AIDS. Participants were African American former or current injection drug users (n=295; 34% female, 45% current drug users and 17% AIDS diagnosed). Outcomes were access to the same medical provider, use of outpatient services and emergency room (ER) use with or without subsequent hospitalization. Controlling for AIDS diagnosis, insurance, current drug use and gender, access to the same medical care provider was associated with more females in one's support network and more network sources of emotional support, financial support and instrumental assistance. Adjusting for confounders, outpatient service use was associated with more female support network members and more sources of emotional support. Controlling for participants' drug use and insurance, sub-optimal emergency department use was associated with greater number of active drug users in one's support network. Contrary to other study findings, having a supportive sex partner was associated with lower access to medical care, and kin support was not associated with medical service use. Results indicate that specific sources and forms of social support had differential influences on the sample's utilization of medical services. The findings suggest that promoting HIV-positive African American injection drug users' support network functioning may help improve HIV medical services utilization among this medically underserved population.