An important first step in the initiation of carcinogenesis by polycyclic aromatic hydrocarbons (PAH), is the formation of a covalently bound adduct between the metabolized PAH and one or more deoxyribonucleic acid (DNA) bases. In vivo concentrations of these adducts are typically ∼1 adducted base per 10⁸ normal DNA base pairs. Methods of generating high resolution fluorescence spectra of adducts at these levels will be described. Methods of overcoming factors such as photochemistry and nonphotochemical hole burning which limit detection limits will be described. By generating line narrowed fluorescence spectra, it is possible to spectrally distinguish between various adduct possibilities.