Over the last century, England, along with most other developed countries, has introduced a wide range of services designed to promote the satisfactory development of its children. Services such as physical and mental health care, dental care, and education are universally available and, despite a flourishing private sector, are still largely delivered, without charge, by public agencies. Nevertheless, of the eleven million children and young people under eighteen years of age in England today, about four million are thought to be vulnerable in that they "would benefit from extra help from public agencies in order to make the best of their life chances" (Department of Health, Department for Education and Employment and Home Office, 2000:2). Of these, 381,500 are defined as children in need, that is, children whose vulnerability is such that they are unlikely to reach or maintain a satisfactory level of health or development, or those whose health and development will be significantly impaired without the provision of additional services (Children Act 1989, Section 17.10). Children Act 1989, which introduces the concept of children in need, also lays on local councils an obligation to provide these additional services, generally through their social services departments, although working closely with other agencies. While it is possible to trace the development of child welfare services in Britain over the last century, it is only over the past twenty years or so that serious attempts have been made to evaluate their outcomes or effectiveness. The introduction of outcome-based evaluation of children's services is, as this book shows, a developing initiative throughout the Western world; in Britain it has been particularly engendered by a loss of confidence in the welfare state, a perceived lack of accountability of public services accompanied by rising costs, and a thriving consumerist movement that demands that services meet the requirements of users (Parker, Ward, Jackson, Aldgate & Wedge, 1991). The systematic evaluation of children's services is part of a much wider movement to introduce outcome-based accountability into all public sector services: health, education, transport, social security and now social services are all increasingly required to provide demonstrable evidence of satisfactory delivery and proof that public money is being well-spent. Within the above context, this chapter explores the introduction of outcome-based evaluation in services for children in need at both micro and macro levels and considers the issues raised by initiatives such as the Looking After Children project, a methodology designed to help practitioners and their managers assess outcomes for children placed in out-of-home care (Ward, 1995), and the "Performance Assessment Framework" (Department of Health, 1996b)- a series of performance indicators for all "personal" social services required annually by government and published in the national press.(1) Poor implementation and problems with management information systems have meant that the link between aggregate and individual data has sometimes been lost, a situation that a new Integrated Children's System aims to redress.