The rate coefficients and product yields for the reactions of CF3O- with ClONO2, HNO3, HCl, N2O5, So(2), HI, and H2O were measured at 295 K and similar to 0.4 Torr using the flowing afterglow technique. The reactions of CF3O- with HO(2)NO2 and H2SO4 were also studied qualitatively. CF3O- reacts rapidly with ClONO2, HO2NO2, SO2, and HCl by only fluoride transfer and with HNO3, HI, and H2SO4 by both fluoride and proton transfer. CF3O- also reacts with HI to form IF2- and with N2O5 to produce NO3-. CF3O- undergoes a slow clustering reaction with H2O and is transformed within water clusters into F-. HF and F-.(HF)(2). CF3O- is unreactive with CH3NO3, CH3C(O)O2NO2, O-3, NO2, CO2, and O-2. These results demonstrate that CF3O- is an excellent candidate as a reagent ion for the selective detection of ClONO2, HCl, and HNO3 in the upper troposphere and stratosphere with a chemical ionization mass spectrometer. The observed reaction of CF3O- with H(2)0 within water clusters indicates that CF3O- will hydrolyze in aqueous solution to form F-, HF, and CO2. This provides insight into the mechanism for the heterogeneous loss of CF3OH in the atmosphere.