This chapter reflects on the normative, empiricist, and interpretive considerations researchers are facing in the process of researching ageism. The starting point of this study was a doctoral dissertation that, by triangulating data, methods, and theory, explored how ageism is manifested in the lives of older people (Snellman 2009). Such a research endeavour is warranted by system justification theory, arguing that support for an ageist structure of society is sometimes strongest among individuals who are most harmed by it (Jost et al. 2004). A large and increasing number of ageism studies report on empirical data; however, these studies are rarely explicitly related to epistemological and ontological questions. Little attention has previously been devoted to the philosophy of science aspects of ageism and therefore there is a gap in what we know about the wider scope of challenges in researching ageism and how we view and understand ageism in our world.One way to devote attention to the philosophy of science aspects of ageism is to focus on the normative, empiricist, and interpretive (Howarth 2000) considerations and choices we as researchers are forced to make during the research process. In short, these considerations enable researchers to (a) take a standpoint against and strive to change negative ageist consequences in society (normative); (b) observe accurately and show how ageist elements are related in a narrow context (empiricist); and (c) observe, show, understand, and reflect critically on how ageist elements are related in a wider context (interpretive).Among the myriad of choices to be made is the choice of what definition of ageism to use in any given case. This chapter demonstrates different types of ageism definitions. These are influenced by normative, empiricist, and interpretive