Rate coefficients for the reactions of FC(O)O radicals with NO, NO2, O-3, O(P-3), CH4, and C2H6 were measured as a function of temperature and total pressure in the range 235-293 K and 9-210 mbar (N-2) FC(O)O radicals were generated using the excimer laser photolysis of bis(fluoroformyl) peroxide (FC(O)OO(O)CF) at 193 nm. Time-resolved detection of FC(O)O was achieved by absorption measurements in the 3(0)(5)-band around 617.5 nm using a tunable narrow band ring dye laser as a light source. At this wavelength the absolute decadic absorption cross section was found to be sigma(FC(O)O)(617.5) = (7.1 +/- 2.6) x 10(-18) cm(2). The following rate coefficients were determined : k(8)(FC(O)O + NO --> CO2 + FNO) = (3.8 +/- 0.5) x 10(-11) cm(3)/s, independent of temperature and pressure, k(9,infinity)(FC(O)O + NO2 --> products) = (5.3 +/- 1.2) x 10(-12)(T/300)(-(2.5 +/- 1)) cm(3)/s, k(11)(FC(O)O + O-3 --> products) less than or equal to 2.5 x 10(-14) cm(3)/s at 293 K, k(14)(FC(O)O + O(P-3) --> products) = (8.8 +/- 2.0) x 10(-12) cm(3)/s at 293 K, k(18)(FC(O)O + CH4 --> products) less than or equal to 4 x 10(-18) cm(3)/s at 293 K, and k(19)(FC(O)O + C2H6 --> FC(O)OH + C2H5) = (1.15 +/- 0.75) x 10(-13) exp[(-1830 +/- 280 K)/T] cm(3)/s. It is concluded that the reactivity of FC(O)O toward these reagents resembles that of the NO3 radical. The reactions involving NO,represent the dominant reactive removal pathways of FC(O)O under all atmospheric conditions. However, even these reactions are not competitive with the photochemical degradation of FC(O)O in the sunlit atmosphere. The effect of FC(O)O chemistry on the stratospheric ozone layer is negligible.