Little is known about the effectiveness of outreach interventions to engage and retain underserved populations living with HIV in stable, primary medical care. This study provided an opportunity to adapt a patient navigation model first developed for cancer care to assess its effectiveness with HIV-infected disadvantaged populations. Four grantees from the Health Resources and Services Administration (HRSA)-funded Outreach Initiative developed and successfully implemented navigation-like interventions. We examined the effectiveness of these interventions in decreasing barriers to HIV primary medical care and improving health outcomes. The conceptual framework laid out in the 1993 Institute of Medicine report Access to Health Care in America provided a valuable heuristic for guiding the analysis, and we used the model to select measures for the study. A reduction in barriers, improvement in mediators, and improved health outcomes were observed over the 12-month intervention period. Structural barriers to HIV care and provider engagement were significantly associated with health outcomes. Based on study results, we propose that an adapted navigation approach referred to as "HIV System Navigation" has promise for improving access to HIV care and warrants further development.