The objective of this study was to evaluate a São Paulo state public school drugs and Aids prevention project. The analysis was developed considering the diversity and complexity of contemporary drug use and the school role, as a socialization agency, always historically determined. The conceptions analyzed are conceptions about drugs; the relation between drugs and Aids - as a possible consequence to the health-illness process and prevention objectives. The analysis was based on documents, the statements of program supervisors, school teachers trained by the program and students who participated in the program activities. The conclusions presented have implications for public policies related to drugs and Aids prevention.