The qualitative research described in this article aims to explore the dynamics of routine public health practice and policy within two local health systems. Using a theoretical framework drawn from social science and management literatures on 'communities of practice' (Wenger, 1998), we seek to illuminate the values and ideas that shape the way in which public health practice and policy making is 'done' on a routine basis. In particular, we suggest that people's narratives about their daily work resonate with the concepts of engagement, peripheral participation and marginalisation used in the communities of practice literature.