This article focuses on some of the issues that shape understandings of professional practice in the rapidly expanding context of children's centres in England. Drawing on data from an ESRC-funded project exploring practitioners' understandings of quality and success, the perspectives of 115 practitioners working in 11 Sure Start Children's Centres are presented. The findings indicate that the practitioners' definitions of quality and success are influenced by contextual elements, such as the organisational climate in which they work, as well as the wider political agenda and their individual histories. Putting practitioners' understandings of quality into practice presents challenges on a number of levels as they search for new ways of working to provide "joined up" provision that will work for children and their families as required by current policy. (Contains 1 table and 1 note.)