Background: This article is concerned with professional learning within multi-agency settings. Since the publication of the government document "Every child matters" in 2003, professionals involved in working with children and young people have been moving into newly organized services that are required to deliver improved services for vulnerable children and their families. Although new ways of professional working are described in the plethora of government guidance that has followed "Every child matters," there has been little examination of how this is being achieved in different teams around the country. Purpose: This paper describes a current national research project, "Learning in and for Inter-agency Working", which is investigating new ways of learning that develop, while teams of professionals work together around children and young people who are at risk of social exclusion. Programme description: The research project is theoretically based and draws upon sociocultural and activity theory research to understand the practices that develop within the different agencies involved. The paper describes the derivation of the theory and the particular aspects of activity theory that are central to the project. In particular, the use of developmental work research (DWR), as the method of intervention with a number of local education authorities, is described and explained. Sample: Some of the early work undertaken within phases 3 and 4 of a five-stage project which began in 2004 and ends in 2007 is described. Five different inter-agency teams of professionals working as part of Children's Services, from different geographical locations in England are the participants in the study. Design and methods: The research uses activity theory to structure a series of DWR workshops with members of the multi-agency teams. Ethnographic data, including observations and interviews, are collected and form the subject-matter of the workshops. Results: The data gathered are used to facilitate workshops where participants discuss their developing working practices and plan changes. The reporting phase of the project, where the findings across all sites will be analysed and summarized is not until mid-2007. However, early themes emerging from the research are included in the paper. These themes include: issues around co-location and co-working, evolving of professional identities, discussion of divisions of labour and professional expertise. These are described and illustrated using data from the research project. Conclusions: As this is still "work in progress" no firm conclusions can be drawn. However, it has become clear that new ways of thinking about professional working with children and families is necessary as old ways of working do not necessarily provide better outcomes for children. (Contains 4 figures, 1 table and 1 note.)