Some children respond to social rejection in ways that undermine their relationships, whereas others respond with more equanimity. This article reports 3 studies that test the proposition that rejection sensitivity--the disposition to defensively (i.e., anxiously or angrily) expect, readily perceive, and overreact to social rejection--helps explain individual differences in response to social rejection. Data were from urban, minority (primarily Hispanic and African American) fifth to seventh graders. Study 1 describes the development of a measure of rejection sensitivity for children. Study 2 provides experimental evidence that children who angrily expected rejection showed heightened distress following an ambiguously intentioned rejection by a peer. Study 3 shows that rejection sensitive children behaved more aggressively and experienced increased interpersonal difficulties and declines in academic functioning over time.