The kinetics and mechanisms of the OH- and Cl-initiated oxidation of two unsaturated HFCs, C4F9CHCH2 and C6F13CHCH2, were investigated. The kinetic study was performed as a function of pressure and temperature for the OH reactions and as a function of pressure at 298 K for Cl atom reactions. The rate constants obtained are (in units of cm3 molecule-1 s-1): k(OH + C4F9CHCH2) = (8.5 +- 1.4) 10-13 exp[(139 +- 48)/T] and k(OH + C6F13CHCH2) = (1.3 +- 0.5) 10-12 exp[(31 +- 124)/T] in the temperature range 233372 K; and k(Cl + C4F9CHCH2) = (8.9 +- 1.0) 10-11 and k(Cl + C6F13CHCH2) = (9.1 +- 1.0) 10-11 at 298 K. The OH and Cl reactions rate constants were found to be independent of pressure in the range 10760 and 1560 Torr, respectively. The mechanistic study was performed in air at atmospheric pressure, in the presence or absence of NOx. CO and COF2 have been identified as the major secondary products of both OH- and Cl-initiated oxidation of the HFCs. However, there is evidence for the formation of different primary products: aldehydes (C4F9CHO and C6F13CHO) in the OH oxidation of the HFCs and ketones (C4F9C(O)CH2Cl and C6F13C(O)CH2Cl) in the Cl oxidation. This suggests that the oxy radicals, precursors of these carbonyl compounds, behave differently. The beta-hydroxyoxy radicals C4F9CH(O)CH2OH and C6F13CH(O)CH2OH decompose, whereas the beta-chlorooxy radicals C4F9CH(O)CH2Cl and C6F13CH(O)CH2Cl react with O2. These results are consistent with the significantly higher activation barrier for the decomposition of the beta-chlorooxy, compared to that of the beta-hydroxyoxy radicals.