This paper presents a summary of the first survey of public library authorities in the UK to explore Sunday opening, undertaken in 2007 as part of the Clore Leadership Programme. It provides a snapshot of Sunday opening practice, set against a context of societal, economic, and policy developments, and examines whether Sunday opening furthers the appeal and use of libraries, and strengthens libraries' place as centres for community engagement. There is considerable variation in practice across the UK. The most common barriers found to Sunday opening were concerned with costs and staffing issues. Two-thirds of respondents who open on Sunday reported increased use as a result of doing so. Critical success factors identified were the location of branches, making an "offer" to attract users, appropriate staffing, and motivation. (Contains 7 figures, 2 tables, and 3 notes.)