This article summarizes two decades of research about family, and especially parental, influences on the risk of adolescents becoming pregnant or causing a pregnancy. Research findings are most consistent that parent/child closeness or connectedness, parental supervision or regulation of children's activities, and parents' values against teen intercourse (or unprotected intercourse) decrease the risk of adolescent pregnancy. Largely because of methodological complexities, research results about parent/child sexual communication and adolescent pregnancy risk are very inconsistent. Residing in disorganized/dangerous neighborhoods and in a lower SES family, living with a single parent, having older sexually active siblings or pregnant/parenting teenage sisters, and being a victim of sexual abuse all place teens at elevated risk of adolescent pregnancy. Several biological factors (timing of pubertal development, hormone levels, and genes) also are related to adolescent pregnancy risk because of their association with adolescent sexual intercourse.