Ever increasing demands for accountability, together with the proliferation of lists of evidence-based prevention programs and policies, led the Society for Prevention Research to charge a committee with establishing standards for identifying effective prevention programs and policies. Recognizing that interventions that are effective and ready for dissemination are a subset of effective programs and policies, and that effective programs and policies are a subset of efficacious interventions, SPR's Standards Committee developed overlapping sets of standards. We designed these Standards to assist practitioners, policy makers, and administrators to determine which interventions are efficacious, which are effective, and which are ready for dissemination. Under these Standards, an efficacious intervention will have been tested in at least two rigorous trials that (1) involved defined samples from defined populations, (2) used psychometrically sound measures and data collection procedures; (3) analyzed their data with rigorous statistical approaches; (4) showed consistent positive effects (without serious iatrogenic effects); and (5) reported at least one significant long-term follow-up. An effective intervention under these Standards will not only meet all standards for efficacious interventions, but also will have (1) manuals, appropriate training, and technical support available to allow third parties to adopt and implement the intervention; (2) been evaluated under real-world conditions in studies that included sound measurement of the level of implementation and engagement of the target audience (in both the intervention and control conditions); (3) indicated the practical importance of intervention outcome effects; and (4) clearly demonstrated to whom intervention findings can be generalized. An intervention recognized as ready for broad dissemination under these Standards will not only meet all standards for efficacious and effective interventions, but will also provide (1) evidence of the ability to "go to scale"; (2) clear cost information; and (3) monitoring and evaluation tools so that adopting agencies can monitor or evaluate how well the intervention works in their settings. Finally, the Standards Committee identified possible standards desirable for current and future areas of prevention science as the field develops. If successful, these Standards will inform efforts in the field to find prevention programs and policies that are of proven efficacy, effectiveness, or readiness for adoption and will guide prevention scientists as they seek to discover, research, and bring to the field new prevention programs and policies.