A study was undertaken to ascertain the feasibility of testing ingredients added to cigarettes for their potential to change the relative health risks of smoking. The Life Sciences Research Office (LSRO), a nonprofit research organization, enlisted a Committee of experts to review the literature and related data to determine whether methods for testing could be devised to assess whether cigarettes with additives changed premature mortality and morbidity relative to cigarettes without additives. The Committee is considering the methods of producing cigarettes, the ingredients that have been used in the manufacture of cigarettes, the biological endpoints, and current and potential methodologies for evaluating the risks of the ingredients and their pyrolysis products. Also, comments at a public meeting will be considered. The limitations of testing will be discussed in the Committee's report. The Committee and LSRO scientists have convened six times and reviewed more than 750 publications, including clinical studies, government reports and books. To date, the Committee considers that a review of the effects of non-tobacco ingredients added to cigarettes, while challenging, is scientifically achievable and potentially useful for public health considerations. This report will provide a foundation for future work to discern relevant tests for cigarette additives and generate criteria for research conditions. Philip Morris U.S.A commissioned the project.