Interpersonal trust reflects a vital component of all social relationships. Trust has been linked to a wide variety of individual and group outcomes in the literature, including personal satisfaction and motivation, willingness to take risks, and organizational success (Dirks & Ferrin, 2001; Pratt & Dirks, 2007; Simpson, 2007). In this dissertation I tested a new conceptual model evaluating the roles of attachment, propensity to trust, perceived similarity of trustee to self, and social exchange processes in trust development with randomly assigned, same-sex undergraduate roommates. Two hundred and fourteen first-year students (60% female, 85% Caucasian, mean age = 18) at a large south-eastern university completed self-report measures once per week during the first five weeks of the fall semester. Perceived similarity measured the second week of classes and social exchange measured three weeks later combined to provide the best prediction of participants' final trust scores. Attachment and propensity to trust, more distal predictors, did not have a significant relationship with trust. This study demonstrated that trust is strongly related to perceived similarity, as well as social exchange. A prime contribution of this study is the longitudinal, empirical test of a model of trust development in a new and meaningful relationship. Future work may build on this research design and these findings by focusing on early measurement of constructs, measuring dyads rather than individuals, and incorporating behavioral measures of trust.