This study examined the relationship between neighborhood safety during adolescence and risk of sexually transmitted diseases during young adulthood among African Americans. The study found that African American adolescents who reported living in safer neighborhoods were less likely to have multiple sex partners or a chlamydia infection as young adults. Additionally, adolescent delinquency like selling drugs predicted later chlamydia infection. The results suggest public health policies should focus on improving neighborhood safety to help reduce racial disparities in sexually transmitted diseases.