Data are used from a random sample of African American families in impoverished Chicago neighborhoods to address two questions: How well do modeling, supervision, and marital transition hypotheses explain the relationship between family structure and early sexual debut and pregnancy for disadvantaged Black female adolescents? Do higher levels of social support from parents and neighborhood adults decrease the risk of sexual activity for youth in poor communities? Support for each hypothesis is contingent upon the family transition experienced and specific sexual outcome examined. Living in any type of married household reduces the risk of sexual debut and pregnancy. Stronger parent-child relationships are associated with delayed sexual onset, whereas the risk of pregnancy is reduced when adolescents report more working adults in their social networks.