Most accounts of affect and motivation in the science education literature have discussed them as relevant to, but distinct from, disciplinary pursuits. These include Pintrich's seminal work on affective and motivational factors in learning science (P. R. Pintrich, 1999, 2003; P. R. Pintrich & E. De Groot, 1990; P. R. Pintrich, R. W. Marx, & R. A. Boyle, 1993). Our purpose here is to build on those ideas, drawing as well on accounts of scientists' practices (e.g., H. E. Gruber, 1974; E. F. Keller, 1983) and of students' taking up of disciplinary pursuits (R. A. Engle & F. R. Conant, 2002; R. Lehrer, 2009; M. Scardamalia & C. Bereiter, 1991, 2006) to propose that affect and motivation are inherent in the disciplinary practices of science. Thus, we introduce notions of epistemic affect and epistemic motivation, and we illustrate how these are evident in a case study of a student we have followed from 4th to 7th grade. We consider how this perspective aligns with and contributes to research on interest (e.g., S. Hidi, 2006; S. Hidi, K. A. Renninger, & A. Krapp, 2004; C. Sansone, 2009), and we discuss implications for research and instruction in science education. We argue that part of what should happen in the science class is to cultivate students' feelings and motivations within the discipline.