Evaluating any health promotion initiative (education, prevention, etc.) has become an essential practice. How should one go about it? How can one assess a change in behavior when it cannot be quantified? The feature article in this issue of *La Santé de l'homme* addresses this question through analyses and practical case studies. Twenty French-speaking experts (from France, Canada, and Belgium) present a step-by-step guide and case studies. The feature’s conclusion: evaluation is essential and possible, but it requires adherence to a highly rigorous protocol. A useful feature and a valuable tool for training.