The proposed research examines the links between belief certainty and several important phenomena, including error in person perception, stereotyping, and low self-esteem. Section I follows up on preliminary studies of dating couples and college roommates indicating that as time and involvement in their relationships increase, they become increasingly certain of their beliefs about their partners with no concomitant increase in the accuracy of these beliefs. It is proposed that these effects exemplify a more general set of phenomena in which factors that make our beliefs richer foster confidence but not necessarily accuracy. The proposed studies will test this hypothesis and identify its range of applicability. Section II focuses on whether or not the model of belief certainty developed in Section I applies to social stereotypes. One study attempts to resolve an apparent contradiction between my model and past research on the certainty of social stereotypes. Another study will test the hypothesis that unmitigated losses of belief certainty increase prejudice. Yet another study will consider the counter-intuitive notion that providing prejudiced people with support for a stereotype may increase their tendency to individuate a member of a stereotyped group. The final study in this series will test the hypothesis that temporary loses in self-certainty within some domains will make people more likely to confirm the stereotype-based expectancies of perceivers. The third and final set of studies will examine the antecedents and consequences of self-certainty. Two studies will examine the cognitive and motivational antecedents of self-certainty. Another study will follow up on preliminary evidence that self-uncertainty and the low self-esteem it theoretically fosters can be eliminated by bolstering people's sense of self-certainty through confirmation of their negative as well as positive self-views. Studies are proposed to examine more directly the hypothesized confidence-bolstering effects of information that confirms people's self-views and specify how increasing self- certainty bolsters self-esteem.