Food insecurity and HIV/AIDS are intertwined in a vicious cycle that heightens vulnerability to, and worsens the severity of, each condition. We review current knowledge and research priorities regarding the impact of food insecurity on HIV transmission risk and clinical outcomes. Observational studies suggest that food insecurity is associated with increased HIV transmission risk behaviors and decreased access to HIV treatment and care. Among individuals receiving antiretroviral therapy (ART), food insecurity is associated with decreased ART adherence, reduced baseline CD4 cell count, incomplete virologic suppression, and decreased survival. Integration of food security interventions into HIV/AIDS treatment programs is essential to curtail the HIV/AIDS epidemic and improve health and quality of life among those infected. Longitudinal research applying validated measurement tools is needed to better understand the mechanisms through which food insecurity adversely impacts HIV transmission, treatment, and care. Research should compare the effectiveness of various food assistance and livelihood strategies.