Inhalants are solvents or volatile anesthetics that are subject to abuse by inhalation. Most are central nervous system (CNS) depressants, but some are convulsants. As a class they are characterized by high vapor pressure and significant solubility in fat at room temperature. Vapors and gases have been inhaled since ancient times for religious or other purposes, as at the oracle at Delphi. Experimentation with inhalants did not occur to any significant extent until after the discovery of nitrous oxide and the search for volatile anesthetics commenced in earnest. Arguably the most toxic of abused substances, inhalants can produce a wide range of injuries, depending on the chemical constituents of what is inhaled. Many are very complex mixtures formulated for a specific purpose, or are used because they are the least expensive alternative, or both. Thus their purity and safety are in no way comparable with those achieved by...