This chapter examines the meaning of ‘data’ in the context of educational research and its relationship to theory and practice in education. It focuses on three research strategies and analyses their different ways of understanding data and method, the different implications of these for theory-building and the different relationships they assume between the researcher and the subjects of their research. Experimental researchers adopting positivist frameworks1 carefully separate out their values from the data they collect and argue that theory-building is always nomological in character, based as it is on the hypothetico-deductive method.2 Survey researchers operating with positivist or post-positivist perspectives (Guba and Lincoln 1994) understand relationshipsbetweenphenomena as havingonly ahighprobabilityof application in other contexts.