Food security and nutrition play an important role in HIV and TB care and treatment, including for improving treatment outcomes, adherence and uptake of HIV and TB care. This AIDS and behaviour supplement on ''Adherence to HIV and TB care and treatment, the role of food security and nutrition'' provides an overview of the current evidence and knowledge about the barriers to uptake and retention in HIV and TB treatment and care and on whether and how food and nutrition assistance can help overcome these barriers. It contains nine papers on three topic areas discussing: (a) adherence and food and nutrition security in context of HIV and TB, their definitions, measurement tools and the current situation; (b) food and nutrition insecurity as barriers to uptake and retention; and (c) food and nutrition assistance to increase uptake and retention in care and treatment. Future interventions in the areas of food security, nutrition and social protection for increasing access and adherence should be from an HIV sensitive lens, linking the continuum of care with health systems, food systems and the community, complementing existing platforms through partnerships and integrated services.