This monograph, Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine, is the 13th report published in the National Cancer Institute's (NCI) Smoking and Tobacco Control Program Monograph Series. One feature of this monograph is that it blends the old with the new. Monograph 7, The FTC Cigarette Test Method for Determining Tar, Nicotine, and Carbon Monoxide Yields of U.S. Cigarettes, covered the history of that protocol and recommended changes in its procedures. Chapter 2 of this publication cites this earlier monograph, brings us up to date on the FTC method, and provides additional suggestions as to what can be done to help alert the public to the dangers of smoking. The examination of the scientific literature on low-tar and low-nicotine cigarettes is not unique to this monograph. Several of the earlier volumes devoted one or more chapters to discussions of the various health aspects of tar and nicotine levels. However, this monograph includes more than just the study of amounts of tar and nicotine. Chapter 5 includes a discussion on the continued health risks to smokers, even those who smoke a low-tar/low-nicotine cigarette, while Chapter 2 describes how changes in the cigarette design affect an individual's smoking habit. Chapter 7 points out how the tobacco companies' advertisements have changed to match the emerging public preference for low-tar/low-nicotine cigarettes. This monograph is unique in another important aspect. For the first time, the authors who prepared the various chapters have had extensive access to the information gleaned from the internal documents of the tobacco companies. The tobacco industry files now open to the public and available on the Internet constitute some 33 million pages of formal and informal memos, meeting notes, research papers, and similar corporate documents. Included are marketing strategies that express the growing concern among the various tobacco companies of the potential loss of new recruits. This concern over the potential loss of market was due to the evolving public opinion that smoking is harmful to health and that it is related to many of the illnesses that smokers experience over the course of their lives. The singular message that has been delivered to the public-smoking causes cancer-is gradually being accepted by more and more people of all ages.