Introduction: Linkage, engagement, and retention in HIV care: essential for optimal individual- and community-level outcomes in the era of highly active antiretroviral therapy.

Engagement in medical care after a diagnosis of human immunodeficiency virus (HIV) infection is essential to initiate lifesaving antiretroviral therapy and facilitate the delivery of important prevention messages for reducing HIV transmission. Failure to engage and be retained in HIV care can be associated with negative outcomes for both the individual and the community. However, many Americans living with HIV infection are, for a variety of reasons, undiagnosed, not in medical care, or not receiving HIV treatment. The articles in this supplement describe the barriers, challenges, and successes in linking HIV-infected patients to expert care in the United States, with a focus on the unique issues faced by specific populations of men who have sex with men, heterosexual men, and women, and the role of the health care system and other structural factors in facilitating or impeding engagement in care.