This ethnographic study explores the underlying structure of the design practices in the Oxford Studio, a design studio course taught at the Massachusetts Institute of Technology Department of Architecture. The study describes elements of the practices in the Oxford Studio and then analyzes the connections among these elements at three levels: (a) surface structure, (b) pedagogy, and (c) epistemology. This analysis suggests spatial organization and scheduling of the Oxford Studio made possible particular pedagogical tools, such as extended desk crits, ongoing cyclical projects, and guest reviews. These pedagogical tools, in turn, both depended on and fostered students' ability to develop expressive ideas about architecture. The Oxford Studio was thus an integrated system of practice built on a foundation of expressive activity. An understanding of how this framework was articulated in the Oxford Studio may be of use in the development of other learning environments using the design studio as a model. (Contains 13 figures.) [The research reported in this paper was supported in part by LEGO Corporation, the Things That Think Consortium at the MIT Media Laboratory, the Waitt Family Foundation, the Foundation for Ethics and Technology, and the Wisconsin Center for Education Research, School of Education, University of Wisconsin-Madison.]