Because of their high-energy density, terpenes could be used as drop-in liquid fuels for ground or air transportation. Two potential terpene fuels, limonene and α-pinene, were oxidized at atmospheric pressure, ina jet-stirred reactor, in the cool flame regime, under fuel-lean conditions and short residence time. Gassamples of the reacting mixtures were collected, analyzed online by FTIR and dissolved in cool acetonitrile for analyzis by high-resolution mass spectrometry (Orbitrap). Direct flow injection or chromatographic separationby ultra-high-performance liquid chromatography and +/- heated electrospray ionization and +/- atmospheric pressure chemical ionization were used to characterize the products of oxidation of limonene and α-pinene. Reaction with 2,4-dinitrophenylhydrazine was used to assess the presence of carbonyl groups in the products.H/D exchange by adding D2O to reaction samples were used for probing the presence of hydroxy andhydroperoxy groups in the products. A large set of oxidation products, including highly oxygenated organic products with five and more oxygen atoms, was observed. Aromatic and/or polyunsaturated products were detected. Van Krevelen plots, computed oxidation state of carbon, aromaticity index, and degree of unsaturation in products were used to rationalize the results and propose reaction pathways.