A series of simulation chamber experiments has been performed on the gas-phase atmospheric oxidation of acenaphthylene with the hydroxyl (OH) radical, ozone (O3) and the nitrate (NO3) radical. Using a relative rate technique the following rate coefficients (in cm3 molecule−1 s−1) were determined at (293 ± 3) K in 1 atm of purified air: (1.09 ± 0.07) × 10−10, (3.99 ± 0.15) × 10−16 and (4.42 ± 0.32) × 10−12 for the reactions with OH, O3 and NO3 respectively. The results indicate that all three oxidants effectively contribute to the removal of acenaphthylene from the atmosphere. A denuder-filter sampling system coupled with off-line analysis by gas chromatography – mass spectrometry (GC–MS) was used to determine the gas- and particle-phase products of these reactions. The major products identified in the reaction with OH were naphthalene-1,8-dicarbaldehyde, 1,8-naphthalic anhydride and a 10 carbon ring-opened dialdehyde. The products identified in the reaction with NO3 and O3 were predominantly oxygenated compounds arising from reaction at the CC bond in the cylcopenta-fused ring of acenaphthylene. The formation of hydroxylated and nitro-PAHs appears to be a very minor reaction pathway. Acenaphthenequinone, a compound known to generate reactive oxygen species at the cellular level, was formed from the reactions of acenaphthylene with OH and NO3. The majority of the oxidation products were found to be distributed between the gas and particle phases, with only acenaphthylenol and oxaacenaphthylen-2-one, relatively more abundant in the particle phase.