Rejection sensitivity (RS) has significant negative impacts on individuals' social cognitions, feelings, and interpersonal behaviors. The present research assessed the hypothesis that the effect of RS on young adults' loneliness is mediated by their tendency to withdraw from social contact so as to avoid possible rejection. Participants completed measures of their RS, their tendencies to engage in social withdrawal to avoid rejection, and their loneliness; as well as measures of their social avoidance and distress, self-esteem, and social self-efficacy. Results confirmed the main hypothesis and also indicated that RS is positively related to social avoidance and distress, and negatively related to self-esteem and social self-efficacy. Implications of the findings for understanding and counteracting RS are discussed.