Absolute state-selected total cross sections for O2+, CO2+, CO+, and C+ resulting from the reaction O+(4S)+CO2 have been measured in the center-of-mass collision energy (Ec.m.) range of 0.2--150 eV. The cross section for O+2 drops off rapidly with increasing Ec.m. and becomes essentially zero at Ec.m.>3 eV. The charge transfer CO+2 is overwhelmingly the major product ion at Ec.m.>0.5 eV. The onsets measured for CO+ and C+ are consistent with the thermochemical thresholds for the formation of CO+ + 2O and C+ + 3O, respectively. ¿American Geophysical Union 1991