Polycyclic aromatic hydrocarbons (PAHs) occur in oil, coal, and tar deposits, and are found as pollution in air, water and soil. Amongst the PAHs are some of the most toxic compounds known. Some of the PAHs are known to be carcinogenic, mutagenic, and teratogenic (linked to birth defects). Because of their wide distribution, it is therefore important to monitor these compounds.1,2 PAHs are by-products of fuel from burning, both fossil fuel and biomass. Incomplete combustion that leads to formation of PAHs might also happen in industrial processes, cooking on barbecues, in fires, and in cigarette smoke. PAHs are also present in food. The highest intake is shown to come from cereals, oils, and fats. Smaller amounts come from vegetables and cooked meat.1,2 The toxicity of the PAHs is highly structurally dependent, and isomers may therefore vary from being nontoxic to very toxic. One PAH compound, benzo[a]pyrene is notable for being the first chemical carcinogen to be discovered (and is one of many carcinogens found in cigarette smoke). PAH compounds of particular toxicological and environmental concern are monitored using internationally recognized methods. The list of priority PAHs varies in different countries. In the United States, the EPA (Environmental Protection Agency) has listed 16 priority PAHs. All of these are available from Chiron as solutions and neat material, in addition to deuterated and fluorinated internal standards.