This article introduces the "Schools and Continuing Professional Development State of the Nation" study (SoNS). Discussion of English policy together with an account of the study's aims and research design provide a context for the other articles included in this special issue. A key assumption behind the research, and the prevailing CPD policy context in England, is that organisational conditions in schools are highly influential in the development of sustained and effective classroom-based, collaborative, inquiry-oriented CPD. Therefore, the aims of the study investigated the range and kinds of support that schools in England provide as well as the range and kinds of CPD activities in which teachers were able to participate. Teachers' professional learning practices and perspectives were researched in relation to three main themes: (a) the benefits, status and effectiveness of CPD; (b) the planning and organisation of CPD; and (c) access to CPD. These questions were explored through a mixed methods design consisting of three strands: (a) literature review; (b) qualitative research (school snapshots); and (c) a national survey of primary and secondary teachers in England. Discussion of processes and procedures of data analysis is followed by a summary of our conceptual model of schools and teachers' CPD. (Contains 1 note, 2 tables, and 1 figure.)