The current research extends three research areas in relational demography: considering deep-level dissimilarity in theory building, assessing dissimilarity perceptions directly in theory testing, and examining the antecedents of dissimilarity perceptions. The results, based on two field studies using diverse samples, demonstrate the effects of enduring personality traits of Extraversion and Agreeableness on an individual's perceived deep-level dissimilarity to coworkers in the workgroup, and the effects of perceived deep-level dissimilarity beyond the effects of actual dissimilarity and perceived surface-level dissimilarity on critical work outcomes, including the individual's overall job attitude, and behaviors of helping, work withdrawal, and actual voluntary turnover. (Contains 1 figure and 3 tables.)