This is the report of a two-day meeting to consider the state of knowledge around behaviour change measures for the prevention of the sexual transmission of HIV. Participants identified four priority issues around this: prevention measures that are effective in concentrated epidemics; analysis of and responses to sexual behaviour involving multiple concurrent partners and other hyperendemic scenarios; gender inequality, inter-generational sex and gender-based violence as major sources of vulnerablity to women and girls in hyperendemic scenarios; and HIV-related stigma and denial as barriers to behaviour change. Analyses of these issues produced a number of recommendations