Health behaviors, such as retention in HIV medical care and adherence to antiretroviral therapy (ART), pose major challenges to reducing new HIV infections, addressing health disparities, and improving health outcomes. Andersen’s Behavioral Model of Health Service Use provides a conceptual framework for understanding how patient and environmental factors affect health behaviors and outcomes, which can inform the design of intervention strategies. Factors affecting retention and adherence among persons with HIV include patient predisposing factors (e.g. mental illness, substance abuse), patient enabling factors (e.g. social support, reminder strategies, medication characteristics, transportation, housing, insurance), and health care environment factors (e.g. pharmacy services, clinic experiences, provider characteristics). Evidence-based recommendations for improving retention and adherence include 1) systematic monitoring of clinic attendance and ART adherence; 2) use of peer or paraprofessional navigators to re-engage patients in care and help them remain in care; 3) optimization of ART regimens and pharmaceutical supply chain management systems 4) provision of reminder devices and tools; 5) general education and counseling; 6) engagement of peer, family, and community support groups; 7) case management; and 8) targeting patients with substance abuse and mental illness. Further research is needed on effective monitoring strategies and interventions that focus on improving retention and adherence, with specific attention to the health care environment.