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.