This article explicates the causal connections between changes in professional jurisdictions and changes in organizational fields. The authors argue that professional projects carry within them projects of institutionalization. They focus attention on the critical but often invisible role that professionals play in institutional work, or the creation, maintenance and transformation of institutions. The key contribution of this article is to explicate the professional project as an endogenous mechanism of institutional change. Based on a review of prior research on institutional change in which professionals play a central role, the authors observe four essential dynamics through which professionals reconfigure institutions and organizational fields. First, professionals use their expertise and legitimacy to challenge the incumbent order and to define a new, open and uncontested space. Second, professionals use their inherent social capital and skill to populate the field with new actors and new identities. Third, professionals introduce nascent new rules and standards that recreate the boundaries of the field. Fourth, professionals manage the use and reproduction of social capital within a field thereby conferring a new status hierarchy or social order within the field.