The ‘big question’ to which RiPPLE’s third theme hopes to contribute is ‘how can investment in water supply and sanitation (WSS) contribute to the government’s wider objectives of economic growth and poverty reduction and what are the implications for WSS sector policy and programming?’. The purpose of this paper is to provide a summary of existing knowledge and current debates in this area and to identify key theoretical and practical challenges which can be addressed under the RiPPLE Growth Theme.