In addition, we decided to include one large multi-site research report commissioned and published by the General Teaching Council of England, Department for Education and Skills. Although not refereed and published in an edited journal, this report conducted by faculty at the Universities of Bristol, Bath and London has been vetted and published by the Department for Education and Skills in England. These 11 studies are the focus of our analysis. The other 44 books or articles provided non-empirical descriptions of existing programmes, reported selfreflective accounts of teachers’ participation, were empirical but unpublished (e.g. papers presented at conferences or dissertations), or were empirical but did not document the essential characteristics of a PLC previously mentioned. These documents were used only as additional support for a comprehensive picture of PLCs.