1. Introduction 2. Formation and Analysis of Tobacco-Specific N-Nitrosamines 3. Synthesis of Tobacco-Specific N-Nitrosamines and Their Metabolites and Results of Related Bioassays 4. Endogenous Formation of Nitrosamines and Oxidative DNA-Damaging Agents in Tobacco Users 5. Recent Studies on Mechanisms of Bioactivation and Detoxification of 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone (NNK), A Tobacco-Specific Lung Carcinogen 6. Epidemiology of Cancer by Tobacco Products and the Significance of TSNA 7. The Biological Significance of Tobacco-Specific N-Nitrosamines: Smoking and Adenocarcinoma of the Lung 8. Comparative Carcinogenicity, Metabolism, Mutagenicity, and DNA Binding of 7H-Dibenzo[c,g]carhazole and Dibenz[a,j]acridine 9. Concluding Remarks