A convenient procedure is described for the quantitation of polynuclear aromatic hydrocarbons (PAH) in water at the nanogram to microgram per liter level. The procedure involves forcing an aqueous sample through a glass microfiber filter connected In series with a 7 × 50 mm C-18 high performance liquid chromatography (HPLC) column. The HPLC column containing the PAH material Is then attached to a C-18 micropacked reverse-phase setup and eluted with an acetonitrile-water gradient. Fractions corresponding to each UV peak are collected and these aqueous-acetonitrile fractions are then Injected directly into a gas chromatograph (GC) equipped with a photolonizatlon detector (PID). Application of this procedure to the study of aqueous chlorination reactions of several polynuclear aromatic hydrocarbons is described. Anthraquinone, a chlorohydrin of fluoranthene, and a monochloro derivative of fluorene, phenanthrene, 1-methylphenanthrene, and 1-methyinaphthalene were identified and quantltated.