This paper reports from the first phase of a study of the inter-professional work of hospital play specialists (HPSs). In this phase, the author aimed to test the utility of Edwards' concept of "relational agency" in inter-professional work in hospital settings. Individual HPSs in two London hospitals were observed for half-day periods, with particular attention paid to inter-professional episodes. At the end of each observation, the play specialists were interviewed by the author about the interpretations of the work of other professionals they brought to these episodes. Inductive analysis of the resulting transcripts suggests that the participants were able to clearly articulate their core expertise and identify the motives underlying the work of a range of other professionals. While the play specialists were motivated by their commitment to children's rights, they identified medical professionals as primarily motivated by treatment outcomes. The paper concludes with discussion of the study's implications for further research and for the preparation of professionals for inter-professional work.