The health promoting school concept is now a well-established framework for the development of health promotion initiatives in schools. Increasingly, attention has focused on the evaluation of school-based health promotion and debate continues over appropriate evaluation designs for the school setting. The authors argue that the case study design provides a useful approach because of its ability to explore the real-life complexities of social contexts using a combination of quantitative and qualitative methods, with a strong emphasis on process as well as outcome measures. The current ENHPS project in Scotland uses a multiple-case study design to evaluate healthy eating initiatives in four schools, based on the principles of the health promoting school. Provides a description of the project and highlights the advantages of case study methodology in addressing key issues around effectiveness of school-based health promotion based on the health promoting school concept.