The literature on teacher education stresses that learning to teach is a developmental process, and therefore, teacher training programs should incorporate a developmental model. We review existing theory and research on the development and training of graduate teaching assistants and apply this perspective to an individual teaching assistant training program at the University of Washington, a large research university. This training program was designed, and has been modified over the past 20 years, to draw on current lines of thinking regarding teaching assistant training practices. Hence, it is organized around the developmental and cognitive issues facing new, and advanced, graduate assistants. Using evaluative program data and feedback from those who have completed this training program, we elaborate upon the usefulness of a developmental approach for the preparation and training of graduate assistants in sociology