Focus groups are an important element of qualitative health research, valued for the forms of knowledge and understanding that emerge from interactions among participants. Common advice for focus groups within health research is to limit the level of variation among respondents to generate comprehensive discussion and shared knowledge. In this article, the authors critically examine this advice, proposing instead that it is useful to acknowledge and, at times, consciously build in heterogeneity across categories of those present. The benefit of doing this is that the interaction thus generated can be used as a space within which to explore differing professional positions and interpretations of issues under discussion. Using research they have done, they explore the practical issues involved in getting different health and social care professionals together and go on to discuss the value and significance of using focus groups to explore the production of professional hierarchies and boundaries.