Interventions to promote health that have been developed over the last 20 years in the relatively new scientific health education tradition, have often been evaluated for their effectiveness. Meta-analyses of effect studies on various subfields, show that these interventions generally have quite substantial effects (mean effect sizes, ES, of 0.46 for primary prevention and 0.49 for secondary prevention and patient education). A planned and systematic application of social science theory in intervention development is a strong determinant of effectiveness. However, learning principles such as rewards and feedback, that have been shown to increase effectiveness, are often not or not adequately applied. Also, too few interventions focus on possibilities to facilitate the desired behavior (such as reminders, financial stimuli, and skills improvement). The potential effectiveness of interventions in practice may be increased by systematic development of adoption and implementation strategies, including the creation of 'linkage systems' between intervention developers and representatives of the target and user systems.