Purpose: Schools necessarily employ elements of a bureaucratic structure to organize the complex task of educating large and diverse groups of students--elements such as a hierarchy of authority, a division of labor, policies, rules, and regulations. Although such a structure is useful, there is a danger that school leaders will overemphasize these elements and so adopt a bureaucratic orientation at the expense of cultivating professionalism in schools. The hypothesis that guided this study was that the degree of teacher professionalism in a school would be related to (a) the professional orientation of principals in their exercise of administrative authority--especially, the extending of adaptive discretion to teachers in the conduct of their work--and (b) the trust evident among various actors in the school community. Research Methods: Data on the five variables under study were gathered via surveys completed by teachers in 80 middle schools in a mid-Atlantic state. Teacher professionalism was assessed using a subscale of the School Climate Index. Four dependent variables were included: the professional orientation of principals and the trust of faculty--namely, in their principals, their colleagues, and their clients (parents and students). The professional orientation of principals was assessed using the Enabling Structure Scale, a scale of teachers' perceptions of how administrative authority is exercised by school leaders; faculty trust was assessed using the Faculty Trust Scales. Findings: The evidence supports the hypothesis positing that degree of teacher professionalism is related not only to the professional orientation of school leaders but also to faculty trust. Faculty perceptions of their colleagues' professionalism were found to be strongly related to a professional orientation in the exercise of authority by administrators, as well as to faculty trust in the principal. In a multiple regression analysis, a professional oriental and faculty trust in colleagues were each found to make an independent contribution to explaining teacher professionalism, whereas faculty trust in the principal and faculty trust in students and parents were found to play a moderating role. Implications for Research and Practice: For schools to foster greater teacher professionalism, school leaders would do well to resist adopting a bureaucratic orientation, with its implicit distrust. They would be better served by exercising their administrative authority with a professional orientation, extending adaptive discretion to teachers in the conduct of their work, and adopting practices that lead to strong trust among school leaders, teachers, students, and parents. (Contains 4 tables and 1 figure.)