A particular approach to collaborative interagency working is that of multiprofessional "communities of practice". Four such groups are described in the context of two action research projects, one relating to primary care and the other to outpatient services for dermatology and ENT. The facilitating features, and the challenges and the potential of working in this way, are discussed, both from the point of view of understanding how knowledge is used and valued in such groups and as a useful mechanism for the development of services that span different professional perspectives and involve consumer interests.