The paper by Lucie Cluver and colleagues in this month's issue of The Lancet Global Health is an important piece of evidence in a sparsely populated field: rigorous evaluation of the impact of interventions that seek to modify the underlying structural determinants of HIV transmission. Almost since the beginning of the epidemic we have been hypothesising about the structural determinants of HIV transmission. Countless pages have been written about the effect of factors such as poverty, marginalisation, human rights abuses, and the status of women on the transmission of HIV.