Theory has been an object of interest for HCI researchers working on questions related to disciplinary identity and maturity. And recently there have been empirical studies of theory use in HCI research publications. These recent studies are crucial for enriching our understanding of how HCI researchers use theoretical knowledge objects like Activity Theory or the Trajectories Conceptual Framework. Moreover, they establish precedent for conducting textual-analytic empirical studies of theory use. However, there are limitations to these recent empirical studies. In this dissertation, I discuss several formative studies conducted during my doctoral career. These formative studies contribute material to the conceptual and theoretical frameworks that I apply in a summative study of theory use in five years of CHI best paper winners (n=90). These studies motivate three primary contributions. First, I provide an empirically grounded description of the richness and diversity of theory use in HCI scholarship. Second, I show that there is a growing collection of nascent HCI theories being proposed and developed. Finally, I suggest an alternative way of framing the HCI research community--one that embraces the diversity and richness of theory use evidenced in its scholarly publications. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]