Relative rate techniques were used to measure k(OH + n-C4F9OC2H5) = (6.4 +/- 0.7) x 10(-14) and k(OH + i-C4F9OC2H5) = (7.7 +/- 0.8) x 10(-14) cm(3) molecule(-1) s(-1) at 295 K leading to estimates of approximate to 0.9 and 0.7 years for the atmospheric lifetimes of n-C4F9OC2H5 and i-C4F9OC2H5, respectively. A pulse radiolysis technique was used to measure k(F + HFE-7200) = (5.6 +/- 2.1) x 10(-11) cm(3) molecule(-1) s(-1) (HFE-7200 = C4F9OC2H5) at 296 K. Using FTIR-smog chamber relative rate techniques the following rate constants were determined at 296 K : k(F + HFE-7200) = (5.5 +/- 1.1) x 10(-11), k(Cl + HFE-7200) = (2.7 +/- 0.6) x 10(-12) and k(Cl + C4F9OC(O)CH3) < 7 x 10(-13) cm(3) molecule(-1) s(-1). Two competing loss mechanisms for C4F9OCHO(.)CH3 radicals were identified in 700 Torr of N-2/O-2 diluent at 296 K; reaction with O-2 and decomposition via C-C bond scission with k(O2)/k(decomp) = 0.026 +/- 0.010 Torr(-1). The Cl atom initiated oxidation of HFE-7200 in N-2/O-2 diluent gives two products : C4F9OC(O)CH3 and C4F9OC(O)H. C4F9OC(O)CH3 is the major atmospheric oxidation product of HFE-7200; C4F9OC(O)H is a minor product. The results are discussed with respect to the atmospheric chemistry of hydrofluoroethers.