Tobacco-specific nitrosamines (TSNAs) represent an important class of toxicants that are analyzed in cigarette smoke and in tobacco and nicotine products. These compounds are carcinogens. Since their levels can be very low, specific methods of analysis were dedicated to their analysis and the more common ones are described in this chapter. Because the nicotine used in e-liquids is commonly obtained from tobacco, the TSNAs can also be present in the aerosols of e-cigarettes, although at a trace level. Volatile TSNAs represent another group of carcinogens that are analyzed in tobacco smoke, but their levels are usually below the detection limit of the methods of analysis.