Irradiations of diluted wood smoke were conducted to assess the nature of the changes which are likely to occur to such a complex mixture in the atmosphere. The photochemical simulations were conducted for two distinctive chemical conditions: (1) diluted wood smoke alone, and (2) diluted wood smoke with nitrogen oxides (NOx) added to bring the hydrocarbon to NOx ratio more in line with that observed in populated areas. In all simulations, changes in chemistry and mutagenic activity were measured for both the gas-phase and aerosol-bound species. When diluted wood smoke alone was irradiated, the reaction proceeded quickly, but the extent of reaction was severely limited by the lack of NOx. Nevertheless, the mutagenic activity of the vapor phase materials increased measurably. For the experiments with added NOx, the photooxidation process was more complete, and a comparison of the mutagenic potential of the aerosol-bound chemicals with the gas phase products was possible.