This paper explores the role of parents of children with gastro-oesophageal reflux in managing their children's health. It draws on the findings of a qualitative study that looked at the way in which treatment decisions are made in a joint surgical-medical clinic and which showed that the parents of children referred to the clinic play a crucial role in the development and execution of treatment plans. Using Habermas's theory of communicative action, we show how the parents develop an in-depth understanding of the condition and its treatments, combining 'objective world' medical knowledge, 'social world' norms and understandings and 'subjective world' experiential knowledge. We argue that in engaging with different forms of knowledge and with the treatment decisions made in the clinic the parents reason and act in a more or less communicatively rational way. The model of the joint clinic enhances the potential for communicative rationality to develop through its more than usually dialogical approach to decision-making that places emphasis on the parents' expertise and incorporates it into the development of treatment plans. As might be anticipated, however, the clinic also provides much evidence of strategic rationality at work, on the part of both clinicians and parents.