The purpose of this study was to examine and describe the role of trust, a complex and understudied aspect of working relationships, among teachers in smaller learning communities (SLC). Based on a review of the literature, four kinds of interpersonal professional relationships were defined and described from individualism to community. An embedded case study was undertaken in order to describe the relationship and the role of trust in four smaller instructional units within a comprehensive urban high school. The study made use of quantitative surveys, interviews, focus groups, observations, and field documents to identify the existing characteristics of teacher-to-teacher relationships. Trust was defined as the voluntary willingness to be vulnerable to colleagues with the expectation that by doing so, positive outcomes for students and faculty will occur. Findings revealed relationships that could be defined as cooperative but not collegial or communal, and levels of trust were relatively low. These outcomes provide educational administrators and teacher leaders with lessons that may be applicable to other smaller learning communities seeking to improve the interactions and trust levels among faculty. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]