Designing tobacco prevention programs requires a thorough understanding of the network of influences that lead to smoking, whether developmental, physiological, psychological, sociological, or economic in nature. Prevention programs must also be rigorously evaluated and then scaled up so that they can benefit as many people as possible. Selecting the most effective programs would yield a significant return on investment for individuals and society, given the enormous cost of smoking. Regulatory preventive interventions, in schools or healthcare settings, within families, and media campaigns have proven beneficial and have sometimes been associated with a favorable return on investment. Examples are provided, particularly programs available in France. The main challenge is for the overall strategy to adopt a proportionate universal approach—that is, to offer prevention services to everyone, while tailoring them to the needs and specific characteristics of each group (level of education, gender, etc.). [RA]