Background Determining the underlying causes of racial disparities in sexually transmitted infections (STIs) is important. In the USA, rates of the most common STIs range from 5 to 20 times higher for African–Americans compared to Caucasians, and the health consequences of STIs can be serious. Residential racial segregation results in very different contexts for individuals and may be an important determinant of sexual risk. The purpose of this study was to examine how segregation and race interact to impact the age trajectory of sexual risk behaviours.

Methods Using 11 years of data from the National Longitudinal Survey of Youth 1997 (1997–2007) and 2000 Census data, the authors performed three-level hierarchical linear regression to examine the associations between hypersegregation, race and a sexual risk behaviour index among black and white non-Hispanic adolescents as they transition to adulthood.

Results Through most of the teenage years, African–Americans are at higher sexual risk than Caucasians. However, by age 19, Caucasians are at higher risk. Hypersegregation was not associated with increased sexual risk index score on average and did not impact the trajectory of the race–sexual risk association.

Conclusions The authors did not find any evidence that hypersegregation was associated with the sex risk index or that it modified the race–sex risk association as individuals got older. Future studies should examine whether segregation is associated with other causes of STI/HIV acquisition risk, such as sexual network patterns.