Trust agreements are cooperative arrangements supported by the school district and teachers' union leadership to promote local educational reforms. The ability of trust agreements to establish local professional cultures that support innovative teaching in California is examined in this paper. Included are: (1) an outline of the logic that links labor relations with conceptions of teaching and the organization of teachers' work; (2) a description of the impact of trust agreements on the support for and substance of teaching that considers the role of project oversight committees, project scope, and teacher leadership opportunities; and (3) an identification of factors that limit program expansion and the development of new professional cultures. (30 references) (LMI)