Bicycle helmet purchase, use, consistent use, and correct use are determined by a complex set of factors. Behavioral theory suggests that they are influenced by the reciprocal association between individual characteristics such as, expectations, skills, attitudes, and beliefs; social influences such as social norms and peer pressure; and environmental factors such as availability, accessibility, and cost. These factors can be influenced through counseling and other interventions. While a review of the literature suggests that many bicycle helmet programs have not been planned using behavioral models and knowledge from the behavioral sciences, many studies include information that supports behavioral principles. This paper describes the behavioral principles and their application to the problem of increasing bicycle helmet use. Recommendations for practitioners are included.