For more than a decade, the Substance Abuse and Mental Health Services Administrations Center for Substance Abuse Prevention (CSAP) has supported demonstration programs designed to identify interventions that work with high-risk populations to prevent substance abuse, delay its onset, and reduce substance abuse-related behaviors. Research now confirms that interventions aimed at reducing the risk factors and increasing the protective factors linked to substance abuse and related problem behavior can produce immediate and long-term positive results. Effective interventions share certain principles that guide prevention providers in structuring client services. The principles appearing in this document have been identified through expert or peer consensus efforts such as consensus panels and meta-analyses. Many have also been published in peer-reviewed journals. Appropriate use of these scientifically defensible principles can assist prevention providers in designing services that are both innovative and effective, and in modifying proven models to respond to the specialized needs of individual programs. (Contains 155 references.) (GCP)