The study involved 3,608 students in grades 5 through 12 in 10 schools. The ethnically diverse sample was 50.8 percent male. Students in five experimental conditions viewed sets of six antidrug PSAs and completed an evaluation questionnaire following each PSAs. Those in the control condition viewed a nondrug-related television program. One PSAs consisted of ads that focused on negative consequences of drug use. Two other PSAs were designed to bolster self-confidence in refusing to use drugs. Two additional sets of PSAs also focused on the negative outcomes of drug use, with attention to methamphetamine and heroin. A total of 30 PSAs were assessed according to the students' perceptions of their effectiveness. Perhaps the most important finding of the study was that the perceived effectiveness of the antidrug PSAs varied widely among the students. The most effective PSAs targeted heroin and methamphetamine use, and the least effective targeted marijuana or drugs in general. Further, the perceived effectiveness of the PSAs was significantly related to perceptions of harm, danger, and social norms. This study advises that only those PSAs that can be empirically shown to be significantly more effective than a control program should be selected for use in a national antidrug campaign. Also, it is necessary to determine the causal direction of the relationships that link perceived harm, perceived danger, and perceived social norms to perceived PSAs effectiveness. 4 tables and 23 references