Journal of Behavioral Medicine, Vol. 17, No. 2, 1994 . Testing the Generalizability of Intervening Mechanism Theories: Understanding the Effects of Adolescent Drug Use Prevention Interventions Stewart I. Donaldson,1,3 John W. Graham,’ and William B. Hansen 2 Accepted for publication: November 9, 1993 Outcome research has shown that drug prevention programs based on theories of social influence often prevent the onset of adolescent drug use. However, little is known empirically about the processes through which they have their effects. The purpose of the present study was to evaluate intervening mechanism theories of two program models for preventing the onset of adolescent drug use. Analyses based on a total of 3077 fifth graders participating in the Adolescent Alcohol Prevention Trial revealed that both normative education and resistance training activated the causal processes they targeted. While beliefs about .prevalence and acceptability significantly mediated the effects of normative education on subsequent adolescent drug use, resistance skills did not significantly predict subsequent drug use. More impressively, this pattern of results was virtually the same across sex, ethnic@, context (public versus private school students), drugs (alcohol, cigarettes, and marduana) and levels of risk and was durable across time. These findings strongly suggest that successfil social influence-based prevention programs may be driven primarily by their ability to foster social norms that reduce an adolescent’s social motivation to begin using alcohol, cigarettes, and marijuana. KEY WORDS: school-based drug prevention; normative education; resistance training; social influence; alcohol use; smoking; marijuana use. ‘Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, University of Southern California, Alhambra, California 91803. ‘Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27109. 3To whom correspondence should be addressed at USC Institute for Health Promotion and Disease Prevention Research, 1000 South Fremont Avenue, Suite 641, Alhambra, California 91803-1358. 195 0160-7715/94/0400-0195$07.00/O 0 1994 Plenum Publishing Corporation