People who are sensitive to social rejection tend to anxiously expect, readily perceive, and overreact to it. This article shows that this cognitive-affective processing disposition undermines intimate relationships. Study 1 describes a measure that operationalizes the anxious-expectations component of rejection sensitivity. Study 2 provides experimental evidence that people who anxiously expect rejection readily perceive intentional rejection in the ambiguous behavior of others. Study 3 shows that people who enter romantic relationships with anxious expectations of rejection readily perceive intentional rejection in the insensitive behavior of their new partners. Study 4 demonstrates that rejection-sensitive people and their romantic partners are dissatisfied with their relationships. Rejection-sensitive men's jealousy and rejection-sensitive women's hostility and diminished supportiveness help explain their partners' dissatisfaction.