This report on the health consequences of smokeless tobacco contains an "Introduction, Overview, and Conclusions" section and four major chapters. Chapter 1 defines the various forms of smokeless tobacco that are used in the United States and examines data pertaining to trends in prevalence and patterns of use. Methodological considerations are discussed and research needs are identified. Chapter 2 presents results of a systematic review of the world's medical literature describing experimental and human evidence pertinent to the evaluation of smokeless tobacco as a potential cause of cancer. Consensus summaries of the literature are presented in each of five categories: (1) epidemiological studies and case reports of oral cancer in relation to smokeless tobacco use; (2) epidemiological studies of other cancers in relation to smokeless tobacco; (3) chemical constituents, including carcinogens of smokeless tobacco; (4) metabolism of constituents of smokeless tobacco; and (5) experimental studies involving exposing laboratory animals to smokeless tobacco or its constituents. Chapter 3 addresses the health effects of smokeless tobacco use on the oral tissues through a systematic review of the relevant scientific literature of animal and human studies. Chapter 4 examines the consequences of exposure to nicotine from smokeless tobacco. The report concludes that the oral use of smokeless tobacco represents a significant health risk, can cause cancer and a number of noncancerous oral conditions, and can lead to nicotine addiction and dependence. (NB)