Both cooked red meat intake and chronic inflammation/infection are thought to play a role in the etiology of colon cancer. The heterocyclic amine 2-amino-3-methylimidazo [4,5-f] quinoline (IQ) is formed during cooking of red meat and may be involved in initiation of colon cancer. Reactive nitrogen oxygen species (RNOS), components of the inflammatory response, contribute to the deleterious effects attributed to inflammation on normal tissues. This study assessed the possible chemical transformation of IQ by RNOS. RNOS were generated by various conditions to react with 14C-IQ, and samples were evaluated by HPLC. Myeloperoxidase (MPO)-catalyzed reaction was dependent upon both H2O2 and NO2-. This reaction produced an azo-IQ dimer and IQ dimer along with two nitrated IQ products identified by ESI/MS. 2-Nitro-IQ was not detected. Product formation was inhibited by 2 mM cyanide. Reduction in nitrated products observed with 100 mM chloride was not altered with 0.5 mM taurine. Nitrated products were also produced by other conditions, ONOO- and NO2- + HOCl, which generate nitrogen dioxide radical. In contrast, conditions which generate N2O3, such as diethylamine NONOate, produced only small amounts of nitrated products with the major product identified by MS and NMR as N-nitroso-IQ. MPO activation of IQ to bind DNA was dependent upon both H2O2 and NO2-. RNOS generated by ONOO- and DEA NONOate also activated IQ DNA binding. The nitrated IQ products were not activated by MPO to bind DNA. In contrast, N-nitroso-IQ was activated to bind DNA by MPO ± N02-. HOCl activated N-nitroso-IQ, but not IQ. RAW cells produced N-nitroso-IQ and increased amounts of NO2-/NO3-, when incubated with 0.1 mM IQ and stimulated with lipopolysaccharide and interferon gamma. Results demonstrate chemical transformation and activation of IQ by RNOS and activation of its N-nitroso product by biological oxidants, events which may contribute to initiation of colon cancer.