In March 2004, Stephen Ball and others presented a symposium at the conference of the British Educational Research Association (BERA) on the necessity of theory in educational research. Like Ball, I have observed that theory, not just social theory, is a difficult space and one that divides researchers (those comfortable with theory and those less so), within educational research. It is an aspect of educational research training that rarely receives the attention essential for "quality" educational research. In the context of the contemporary research assessment exercises, it is worth reflecting on the relationship between research informed by social theory and expectations of quality and impact. In this paper I revisit the argument made by Ball and others for the necessity of theory, and discuss its role in framing research questions, informing analysis, and promoting reflexivity on the significance and relevance of research. I illustrate this process by discussing the ways theory can assist in the generation of research agendas and questions. I conclude the paper with an example of how a team of educational researchers from Australia, UK and New Zealand have made use of social theory to inform an Australian Research Council (ARC) funded project investigating the recontextualisation of health knowledge in schools. (Contains 1 endnote.)