Romantic relationships are central in the lives of young people. This paper uses data on romantic relationships from urban youth in the USA to illustrate how using a relationships perspective in HIV/STI and pregnancy prevention programmes broadens the skills and content covered, and contextualises the learning to enhance relevance and use. Self-report survey data were collected using electronic handheld devices for a school-based randomised trial. The survey sample includes 911 young people (mean age = 12.4 years) representative of their schools. Logistic regressions explored associations between selected sexual behaviours and relationship characteristics. For all participants, having more boy/girlfriends, dating alone, ever touching and ever having had oral sex were associated with an increased likelihood of having vaginal sex. Among young people with current partners, having a partner three or more years older, length of relationship and ever having oral sex were associated with an increased likelihood of having vaginal sex. The study data confirm the importance of accounting for relationships in sexual risk reduction programmes, and provide avenues for enhancing the relevancy of typical school-based prevention programmes.