This article documents the prevalence of self-reported substance use among White and American Indian adolescents enrolled in seventh grade (ages 12 through 13) in 1997 in a Northern Plains state. Data were collected by self-administered questionnaire preceding adolescents' participation in a randomized field trial of Project Alert, a seventh and eighth grade substance use prevention curriculum. Rates of lifetime and past-month use of cigarettes and marijuana were higher among American Indians than among Whites of the same gender. American Indian girls exceeded American Indian boys as well as White girls and White boys on lifetime and past-month use of cigarettes and marijuana as well as alcohol and inhalants; differences on cigarette and inhalant use reached statistical significance. These findings add to the sparse literature on substance use among adolescents as young as 12 through 13 years old and underscore the importance of examining gender-specific substance use patterns early in adolescence.