Since 1997, there has been a growing interest in the UK in reducing health inequalities, regenerating disadvantaged neighbourhoods and ending cycles of social exclusion. Large sums of money have been invested in large social programmes, mostly designed to be implemented in partnership with local communities. This policy paper asks to what extent these programmes are evidence based, what is being done to find out whether they work, and how far their evaluations are helping to build knowledge to inform policy and practice in the future. The contents of the paper are informed by a transatlantic seminar series, a programme of interviews with commissioners, policy leads, academic evaluators and paid workers in five major social programmes in the UK, an examination of case studies and a literature review.