Although called “e-cigarettes,” e-cigarettes are not cigarettes at all. They contain no tobacco, and there is no combustion. Constituents of tobacco cigarette smoke and e-cigarette vapor are markedly different. Tobacco smoke is produced by combustion of organic material, which generates the particulates and gases with the greatest toxicity. Thousands of toxicants, including carcinogens, have been identified in tobacco smoke.4 In contrast, e-cigarette vapor contains trace to no detectable toxicants, such as volatile organic compounds, carbonyls, tobacco-specific nitrosamines, and polycyclic aromatic hydrocarbons.5 The level of any of these toxicants in e-cigarettes, if detectable at all, is orders of magnitude less than that found in tobacco cigarette emissions. Even in licensed nicotine replacement therapies (NRTs) already approved by the US Food and Drug Administration (FDA), such as gum or patches, trace levels of tobacco-specific nitrosamines and metals are present.6 Additionally, e-cigarette emissions do not contain carbon monoxide or other toxic gases. e-Cigarette emissions include flavorings, but the principal component is the carrier compound, propylene glycol. Propylene glycol is present in several FDA-approved injectable medications, and aerosolized propylene glycol is being evaluated for delivery of inhaled medications.7 In summary, although not everything is known about e-cigarette vapor, the available data support the notion that it is vastly less toxic than tobacco cigarette smoke.