Naphthalene is the most abundant polycyclic aromatic hydrocarbon found in polluted urban areas. Its most important atmospheric loss process is the reaction with OH radicals. In this Letter, we studied the mechanism for the OH-initiated atmospheric photooxidation of naphthalene in the presence of O-2 and NOx, using high-level molecular orbital theory. The profile of the potential energy surface was constructed, and all of the possible product channels were discussed. The theoretical results were compared with the experimental observation. (c) 2006 Elsevier B.V. All rights reserved.