New communication technologies have made an impact on several areas of our everyday life, including the areas of health and health promotion. The Internet provides opportunities for personalized interactive health communication at a much larger scale than is possible in face-to-face communication. It has been suggested that only interactive health-behavior-change Web sites that advise, assess, assist, provide anticipatory guidance, and arrange follow-up have the potential to lead to successful behavior change. Additional factors that may affect the success rate of behavior-change programs are the reach of and the exposure to such programs. This chapter elaborates on all of these factors.