There is no question that principal support is vital to the establishment and maintenance of a quality library media program. The problem is the support flows from trust, and trust flows from understanding. Many principals do not understand what teacher-librarians really do, nor do they appreciate the potential the library media program has for contributing to student and faculty achievement. Principals' perceptions of school libraries and teacher-librarians have been shaped by four interactive forces. The first is their own experiences in school libraries as children, in which they perceived the library as peripheral to the classroom. The second is the effect of their professional training, in which the library's role in curriculum and instruction was consipicuously absent. The third is the nature of the teacher-librarian's work, which is to enable and empower others. The fourth is the low profile teacher-librarians and school libraries have in the professional literature read by teachers and administrators, which prevents them from updating their sense of what the library really is and can do. The cumulative result is that administrators have only a limited and inaccurate understanding of libraries and teacher-librarians. The only way to change principal perceptions is to assault them directly, repeatedly, and from a multiplicity of directions. Reshaping perceptions takes time and effort and commitment. In the meantime, these erroneous perceptions will continue to guide most principals' relationships with school library media specialists.