Reducing tobacco use, especially cigarette smoking, is a public health priority. The American Stop Smoking Intervention Study (ASSIST) was initiated in 1991 to prevent and reduce tobacco use primarily through policy-based approaches to alter the social-political environment. This article describes the conceptual design, research framework, evaluation components, and analytic strategies that are guiding the evaluation of this demonstration research endeavor. The ASSIST evaluation is a unique analysis of the complex relationships between the social context, public health activity at the state level, tobacco use, and individual behavior. The measures of tobacco control activity developed for this evaluation may be useful in ongoing national cancer control surveillance efforts, and the lessons learned will enhance the development of tobacco control programs.