African Americans marry later and are more likely never to marry than Non-Hispanic whites, and consequently high proportions-over two-thirds-of black children are born to unmarried mothers. Prior research shows that economic factors, specifically high rates of unemployment and low earnings among black men, explain some, but not all, of this race gap. The remainder is probably due to social factors we have yet to identify. The social influences on relationship formation are likely easier to measure in adolescence than in adulthood, because adolescents' lives are more tightly controlled by the family and school than parallel institutions control adult lives. We expect that the social factors that contribute to race and ethnic differences in adult relationship formation are evident in adolescence, but few studies have examined adolescent social relationships with the opposite sex except to study sexual behavior. To demonstrate the value of investigating adolescent social experiences, we will examine the associations between the characteristics of adolescents' relationships with the opposite sex and relationship formation in adulthood. Our primary goal is to investigate how adolescent relationships with the opposite sex are shaped by the institutional and social context of schools, using data from the National Longitudinal Survey of Adolescent Health (Add Health) and the high school transcript study, Adolescent Health and Academic Achievement (AHAA). We distinguish two dimensions of adolescent relationships, sexual activity and couple involvement. Couple involvement concerns the degree to which the pair presents themselves to each other and to others as a couple. Most prior research has focused on sexual activity, but a key difference between white and black relationships may be along the couple dimension and the degree to which adolescent sexual relationships are accompanied by couple identification. We will model the association between the social context of schools and these two dimensions of adolescent relationships with the opposite sex. The internal structure of schools shapes the normative climate for sexual and romantic relationships. We characterize the normative climate by observing the attitudes and behaviors of other students. Importantly, rather than assuming that all students share the same social context, we identify subgroups by examining course-taking behaviors and create measures that characterize the attitudes and behaviors of students within these subgroups.