The advent of antiretroviral therapies in 1996 prompted an interest in the role played by ancillary services in improving access to and retention in medical care, particularly since the success of the new therapies is often contingent upon ongoing and appropriate primary medical care. Using self-reported survey data from a longitudinal representative sample of 577 HIV-positive adults in New York City, this paper explores the impact of such supportive services as drug treatment, case management, housing assistance, mental health treatment and transportation on engagement with medical care. The study's principal finding was that specific ancillary services were significantly associated with an increase in an individual's likelihood of entering medical care and maintaining appropriate medical care services for HIV, particularly when the services addressed a corresponding need.