Level of self-control was significantly related to all forms of substance use in race-specific analyses and when controlling for race, as well as when native traditionalism indicators were included. Native-Americans reported low self-control compared to Whites, and the influence of self-control on substance use by Native-American youth persisted regardless of the degree of conditioning into Native-American customs. The effect of self-control on marijuana and serious drug use, however, was significantly greater among Native-American youth compared to White youth. Further, the Native-American youth most attached to their native traditions engaged in greater substance use, even when controlling for the influence of self-control. This suggests that sociodemographic and/or cultural differences between the two groups of youth might be linked to some variation in the effect of self-control on substance-use behaviors. This finding challenges self-control theory's (Gottfredson and Hirschi, 1990) that level of self-control maintains a consistent influence on antisocial and deviant behavior across cultures and other descriptive variables. The authors explain this finding as likely due to the stress of attempting to maintain a native identity while being exposed to the values of White society. Data were obtained from 1,122 White youth and 382 Native-American youth in grades 9 through 12 in 6 Oklahoma school districts. Dependent variables were the use of tobacco, alcohol, marijuana, and hard drugs (cocaine, crack, speed, downers, heroin, LSD, or PCP). Independent variables were self-control, measured by Grasmick et al.'s self-control scale; and native traditionalism, measured by Scott's (1986) native attachment scale. 4 tables, 94 references, and appended descriptive statistics