This paper considers what happens when research-based strategies are attempted outside the context of the original research and questions whether positive findings from research studies can be generalized to real-world settings. Prevention programs within a school system were identified and an activities questionnaire was developed to measure each of the hypothesized factors leading to high implementation. Over 17,000 prevention activities were sampled. Data on the quality of implementation came from 3,700 reports on 14 different types of program activities that were obtained from 550 schools. The results suggest that attention needs to be given to help raise the quality of implementation of prevention programs. In conclusion, there is plenty of room for improvement in the quality of implementation. The effectiveness of prevention activities can most likely be boosted if ways can be found to improve the quality of what schools are already doing. Improving training, supervision, structure, and availability of information can broadly improve the quality of school-based prevention of problem behaviors. The results also suggest that prevention interventions are most likely to be well implemented if they are integrated with the regular school program and initiated by school insiders. (Contains 9 references and 10 figures.) (JDM)