This article examines some of the tensions in the generation of knowledge about water governance and poverty, and the translation of this knowledge into policy and practice. It draws on the experience of the authors in developing a framework for understanding water governance and poverty, their work on a project in Tanzania and their attempts to engage with policy makers. The authors propose that the negotiation of knowledge is a political process shaped both by power relationships and (often implicit) normative values. Such negotiation may be impeded by the contrasting positions of academics as uncertainty creators and policy makers seeking uncertainty reduction. The authors critique instrumental approaches to the generation of knowledge and policy based on the amalgamation of perceived 'success stories' and 'good practice'. They favour instead approaches that attempt to understand water governance arrangements and outcomes for the poor within wider frameworks of negotiations over the allocation of societal resources. This implies the need to rethink the research - policy relationship and to build reflexive knowledge generation into the research-policy interface.