Community-based demonstration projects represent the translation of research findings into practice. This article discusses the scientific basis for demonstration projects and illustrates various principles through two large-scale programs: the Health Promotion and Disease Prevention Research Centers and the Community-Based Public Health initiative. These programs have shown several key components for success, including: building effective partnerships, using existing data effectively, adopting a causal model in intervention design, employing appropriate evaluation techniques, using policy change as an intervention, and utilizing the potential of community groups to foster change among professional partners.