A study has ben carried out using out selected ion flow tube apparatus of the reactions of NO2+ and O-2(+) ions in their vibronic ground states with ten organic species : the hydrocarbons, benzene, toluene, isoprene, cyclopropane, cyclopropane, and n-pentane; the oxygen-containing organics, methanol, ethanol, acetaldehyde, acetone, and diethyl ether. The major objectives of this work are, on the one hand, to fully understand the processes involved in these reactions and, on the other hand, to explore the potential of NO2+ and O-2(+) as chemical ionization agents for the analysis of trace gases in air and on human breath. Amongst the NO2+ reactions, charge transfer, hydride-ion transfer, and termolecular association occur, and the measured rate coefficients, k, for the reactions vary from immeasurably small to the maximum value, collisional rate coefficient, k(c). The O-2(+) reactions are all fast, in each case the k being equal to or an appreciable fraction of k(c), and charge transfer producing the parent organic ion or dissociative charge transfer resulting in two or three fragments of the parent ion are the reaction processes that occur. We conclude from these studies, and from previous studies, that NO2+ ions and O-2(+) ions can be used to great effect as chemical ionization agents for trace gas analysis, especially in combination with H3O+ ions which we now routinely use for this purpose.