In the Zon-programme high priority is given to the development of efficacy and effectiveness of preventive measures, specially in Mental Health. This project will offer empirical evidence on effect predictors in interventions in mental health promotion and mental disorder prevention. Use of knowledge about effect predictors will improve efficacy of interventions.The research will be based on a meta-analysis study and a Delphi study. Research outcomes will be compared with the PREFFI 1.0, an instrument to enhance the efficacy of interventions in health promotion in general, to validate its items for the field of Mental Health. On the basis of this study recommendations for improvement of current items and inclusion of new effect predictors will be made. A revised PREFFI 2.0, will be defined in 2001. In addition, the results will be translated into guidelines for quality and effect management in practice and in recommendations for prevention research policy.