Although researchers often incorporate various measures of ethnicity and ethnic identity (EI) into research about substance use, the relationships among ethnicity, EI, and substance use remain unclear (Marsiglia, Kulis, & Hecht, 2001; Phinney, 1996) . This paper explores whether ethnicity and three EI instruments are useful in predicting substance use outcomes among three samples of ethnically diverse middle school youth. Findings include that age, gender, and/or racial or ethnic group

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... p influenced the strength of EI and that age, sex, and strength of EI influence substance use norms and behaviors. In each case where significant effects were obtained, a stronger sense of EI as measured by two of the instruments predicted more negative attitudes toward, and less use of, alcohol, cigarettes, and marijuana. Implications for preventing substance use among middle school youth by building on and strengthening ethnic identity are provided.