This chapter begins to establish a theoretical framework of what interests are, how interests are represented and organized in the human mind, and where interests are positioned in the nomological network. It reviews that research from educational psychology and vocational psychology, in which interests are conceptualized as states and traits, respectively. The chapter discusses incorporate insights from other fields—notably, behavioral genetics, cognitive psychology, and developmental psychology—to bridge the state and trait perspectives on interests and to develop theoretical propositions that establish an integrative framework. The chapter addresses some of the fundamental issues and presents an overview of new conceptualizations of interests, followed by a discussion of our proposed theoretical framework and a series of specific propositions. Studies on trait complexes and integrative frameworks of individual differences provide a new approach to understanding the nature of interests. Interests and values are similar in that they are both contextualized and involve external objects.