Among the most important developments in substance abuse prevention theory and programming in recent years has been a focus on risk/protective factors as a unifying descriptive and predictive framework. One hypothesis derived from this framework is that the more risk factors a child or youth experiences, the more likely it is that she or he will experience substance use and related problems in adolescence or young adulthood. Risk factors include biological, psychological/behavioral, and social/environmental characteristics such as family history of substance abuse, depression or antisocial personality disorder, or residence in neighborhoods where substance use is tolerated. Protective factors, such as solid family bonds and the capacity to succeed in school, help safeguard youth from substance use. Numerous data collection techniques, such as process evaluations and staff observations, are used to gain knowledge in the substance abuse field. In the past, literature reviews were frequently analyzed to determine whether substance abuse prevention programs worked. Meta-analysis offers a major refinement on that approach. Meta-analysis uses qualitative as well as quantitative methods to produce aggregated results from multiple programs that can be used to study relationships and test hypotheses. While both quantitative and qualitative techniques have important roles to play, their purposes are different. The more quantitative techniques are useful in identifying interventions and contextual factors that influence effectiveness, whereas qualitative techniques are most useful in identifying effective programs and models of intervention. As a result, qualitative techniques can be used to identify both successful program models and prevention principles. Both techniques can be supported by field observation and careful review of complete program documentation. Also both are valuable in developing and deriving principles regarding successful program implementation. 2 figures, 25 references and glossary.