Since the 1950s, interior decoration evolved into interior design. Throughout the 1970s, all of the components for professionalization were in place, but it was not until the 1990s that the final transformation made interior design into a profession. This dissertation documents these changes and posits that is the conflicts inherent in the process of licensure transformed it into a profession. The transformation of interior design is examined through the lens of the theory of professions, especially Andrew Abbott's delineation of transformation through conflict. The historical case studies of the legislative process were of the District of Columbia, which has practice legislation; the Commonwealth of Virginia; which has title legislation; and the State of Ohio, which has no licensing of interior designers as of 2007. Data collection was by interviews with participants of the process of licensure and with the leadership of the interior design community. In addition, primary and secondary documents examined include books, journals, trade magazines, and documents from professional organizations. Specifically, this dissertation addresses these questions: Is interior design a profession? If so, what forces transformed interior design into a profession? And, how is interior design different from architecture? This dissertation posits that interior design is unique from architecture because it developed in home economic programs at state universities during the 1950s, 1960s and 1970s. In this locale, the primary focus of interior design was the micro-environment based on the theory of behavior. This gives students and practitioners a unique viewpoint that allows for the consideration for each end user as integral to the design process. These attributes contribute to the unique qualities of the services interior design offers and separate it from those of architecture. A simplified definition of interior design that I developed is that interior design utilizes the theory of behavior to design spaces in a micro-environment that function at a safe and efficient level for every end user and are aesthetically pleasing. Finally, interior designers need to understand that the strength of their position in the built environment is in the unique services they offers and celebrate their qualities as outlined in this document.Ph. D.