The heterogeneous oxidation of a saturated hydrocarbon monolayer by NO3 was studied. A flow tube reactor coupled to chemical ionization mass spectrometry was used to determine the reactive uptake coefficient of NO3 on these surfaces, and X-ray photoelectron spectroscopy (XPS) was used to investigate surface oxidation and to determine if exposure to NO3 leads to volatilization of the organic substrate. The uptake coefficient of NO3 by an alkane monolayer is about (8.8 ¿ 2.5) ¿ 10-4, which may lead to competitive oxidation compared with OH, due to the higher atmospheric abundance of NO3 under certain conditions. The XPS results are consistent with the formation of 1) C-O groups, 2) ketones or aldehydes, and 3) carboxylic groups. The XPS results also suggest that NO3 does not rapidly volatilize the organic surface: even under extremely polluted conditions, maximum 10% of the organic layer is volatilized.