As a psychologist studying developmental issues in their social context, Barbara Tizard turned her attention to a remarkable variety of research issues with significance for clinicians dealing with children and their families as well as for public policy. These include the importance of play, the development of language, the outcome of children adopted after infancy, and the identity of children of mixed race. In all these areas, she has carefully considered the way in which her findings might influence practice and policy and has often entered public debate on t~e issues. At the same time, there has been a very considerable expansion of research activity relevant to the management and prevention of child psychiatric disorders. In this chapter I consider evidence for the impact of this work.