This chapter seeks to clarify the importance of theory in informing the purposes and design of research. It argues also for the importance of distinguishing research into IT in education from other kinds of research, and the need, in particular, to ground research into IT in theoretical knowledge about the process of innovation. Many researchers assume that the same methods can be applied to any situation, and they tend to see knowledge as a set of established propositions which are equally ‘true’ in all contexts. Paradoxically, those who apply these methods to research into IT in education are often little concerned with ‘theory’ which they tend to dismiss as unimportant and unnecessary when what is needed, as they see it, is systematic application of methods – often surveys involving the administration of questionnaires – to establish facts about the uptake and use of IT, the amount of in-service training delivered to teachers, and the test score results of the students who have been taught in IT-rich classrooms compared with those who have not received this ‘treatment’. This chapter contests this view and argues, with Lewin (1951), that for knowledge to be practical – that is, powerful in changing the social practices of human beings – it needs to be grounded in a coherent body of theory. Moreover, this body of theory should inform the research methodology and methods which generate the knowledge, as well as the analysis of the situations under study.