Deuterated alkyl benzenes, polycyclic aromatic hydrocarbons (PAHs), and N-, S-, O-, and Cl-containing aromatics were prepared using a single reagent containing D2O, DCl, and chromium. The method requires little specialized equipment or synthesis expertise, and results in the exchange of all aromatic protons for deuterium. The isotopic purities of the deuterated products were controlled by the amount of reagent added, and in most cases, isotopic purities of 95% were achieved. Under appropriate conditions of temperature and time, no significant chemical degradation of the aromatic compounds occurred. The method also works well with complex mixtures and large (30 g) quantities of aromatic compounds as demonstrated by the deuteration of a mixture of polychlorinated biphenyls (Aroclor 1254) and a coal-derived anthracene oil.