This paper describes the Self-Evaluation Maintenance (SEM) model of social behavior which consists of three variables: the psychological closeness of another, the relative performance of that other, and the relevance of the performance dimension to one's self-definition. The SEM model is described as involving two processes, the reflection process and the comparison process. Relationships among the three variables are hypothesized, such as the raising of one's own self-evaluation by the good performance of another person close to one's self. Experimental research is discussed which provides support for the hypotheses that when relevance is high the comparison process is more important than the reflection process and that when relevance is low the reflection process is more important than the comparison process. Findings of research on siblings are presented which also give supporting evidence for the model. The implications of this research to psychologists--which involve pro-social behavior, interpersonal relationships, and unit formation--are discussed. The predictions that the SEM model provides for relationships are discussed and the role of affect/emotion in the working of these processes is explored. Five pages of references as well as tables and figures are included. (ABL)