This report by 3ie summarises a systematic review by De Buck and colleagues that examines which promotional approaches are effective in changing handwashing and sanitation behaviour and which implementation factors affect the success or failure of such interventions. The study is the first mixed methods systematic review of behaviour change in sanitation and hygiene, drawing on quantitative and qualitative evidence. It shows that CLTS, in comparison with approaches like social marketing and health messaging, is most effective in improving OD behaviour and latrine use. But there is very limited evidence on sustainability (ie the evidence is not being collected routinely in studies), particularly of approaches to reducing slippage. The review also synthesises evidence on factors enabling and limiting the effectiveness of CLTS and other approaches, which the stakeholder group (comprising some 20 policy and implementation bodies like WSSCC, WSP, Red Cross, DFID etc) said was particularly useful for their work in implementing the approaches in the varying contexts in which they work.