Social projection and self-stereotyping are rival explanations for self-other correspondence, in which people tend to perceive a high degree of similarity between themselves and others. The present research shows that both accounts are correct-that is, that knowledge of the self and knowledge of others are mutually constraining. In Study 1, participants whose self-views were experimentally manipulated revised their judgments of an immediate ingroup. In Study 2, an analogous manipulation of ingroup traits altered participants' self-views. In Study 3, participants who were ascribed a trait readily projected to and stereotyped from their relevant ingroup, but not to or from an outgroup. Finally, Study 4 provides reaction-latency evidence for social projection and self-stereotyping as judgmental processes leading to self-other correspondence. In this task, participants referenced self-knowledge when reaching ingroup-descriptiveness judgments (evidence for social projection) and ingroup knowledge when judging the self (evidence for self-stereotyping). Implications for the debate between protocentric and egocentric accounts of person perception are discussed.