BackgroundSexual minority adolescents are more likely than their heterosexual peers to use substances. This study tested factors that contribute to sexual orientation disparities in substance use among racially and ethnically diverse adolescents. Specifically, we examined how both minority stress (i.e., homophobic bullying) and social norms (i.e., descriptive and injunctive norms) may account for sexual orientation disparities in recent and lifetime use of four substances: tobacco, alcohol, marijuana, and prescription drugs. ProceduresA probability sample of middle and high school students (N=3012; aged 11–18 years old; 71.2% racial and ethnic minorities) using random cluster methods was obtained in a mid-size school district in the Southeastern United States. ResultsSexual minority adolescents were more likely than heterosexual adolescents to use substances, experience homophobic bullying, and report higher descriptive norms for close friends and more permissive injunctive norms for friends and parents. While accounting for sociodemographic characteristics, multiple mediation models concurrently testing all mediators indicated that higher descriptive and more permissive injunctive norms were significant mediators of the associations between sexual orientation and recent and lifetime use of the four substances, whereas homophobic bullying was not a significant mediator of the associations between sexual orientation and recent and lifetime use of any of the substances. ConclusionsDescriptive and injunctive norms, in conjunction with minority stress, are important to consider in explaining sexual orientation disparities in substance use among racially diverse adolescents. These results have implications for substance use interventions among sexual minority adolescents.