Polystyrene films were exposed to radiation of long wavelength (lambda greater-than-or-equal-to 300 nm) and short wavelength (lambda = 253.7 nm) under atmospheric oxygen. Changes in the FTIR spectra of the photooxidized samples were followed, along with several postirradiation treatments including chemical derivatization reactions and HPLC analysis of the low molecular weight fragments that were obtained after extraction by methanol. The absorption maxima which were found in the carbonyl and hydroxyl regions of the infrared were assigned, and the corresponding photoproducts were identified.