Development of trust among organization leaders and staff is important to the formation of successful organizational collaborations. Nonprofit leaders in two rural regions of southern Illinois and the Mississippi Delta demonstrate an awareness of the importance of trust among participants in the collaborations they engage in. Several environmental factors both encourage and constrain the ability of nonprofits in the two regions to form collaborations and build trust among partners. One of these, rural location, is largely considered a positive influence, making it easier for nonprofit leaders to get to know each other and work cooperatively. In addition, other factors such as race relations, government policies and mandates, nonprofit leadership, and organization financial and political resources have powerful effects on creation of collaborations and development of trust.Collaboration is a social exchange involving commitment of knowledge, skills, and emotions by the leaders and staff of participating organizations. It is an "intense form of mutual attachment, operating at the levels of interest, intent, affect and behaviour; actors are bound together by mutually supportive pursuit of individual and collective benefit" (Cropper, 1996, p. 82). Individuals involved in the collaboration must be willing to risk personal and organizational reputations, relinquish a measure of stability and control over their work lives, and enter into unequal exchanges as a partner that is expected to contribute more resources than weaker partners, or a partner willing to risk working with more powerful entities.What binds the individuals and organizations together over time in this social exchange? One important factor is the building of trust relationships among people and organizations in the collaboration. Bonds of trust and consequent reciprocal behaviors help the collaboration survive rough times that Note: The authors wish to thank the Nonprofit Sector Research Fund of the Aspen Institute, which funded this project, thus making it possible. We also express our deep appreciation to the editor of NVSQ and the reviewers of our manuscript for their insightful, instructive comments.