Photolysis of CFCl2CH3 (HCFC-141b) and CFCl2CH3/O-2/N-2 gas mixtures was investigated at 4-60 Torr and 253-321 K by means of UV flash photolysis and time-resolved mass spectrometry. Atomic chlorine was produced by the photolysis of CFCl2CH3. The concentration of Cl so formed was experimentally determined by NOCl trapping of the atoms. Observation of the kinetic growth curve of the CFCl2CH2O radical and growth and decay of ClO permitted a kinetics study of the reactions of Cl and ClO with the peroxy radicals, CFCl2CH2O2 and CH3CFClO2, which were formed following the photolysis of CFCl2CH3 in the presence of oxygen. The peroxy radicals were removed by self-reactions and cross reactions and by reaction with Cl and ClO. The temperature dependence of the rate coefficients of the CFCl2CH2O2 and CH3CFClO2 plus Cl reaction was estimated to be (6.1 +/- 0.3) x 10(-10)e((-779+/-55)/T) and (8 +/- 3) x 10(-11)e((-646+/-69)/T) cm(3) molecule(-1) s(-1), respectively. The rate coefficients for the reactin of ClO with these peroxy radicals were estimated to be (6.0 +/- 0.7) x 10(-12) cm(3) molecule(-1) s(-1) for CFCl2CH2O2 and (4.5 +/- 1) x 10(-12) cm(3) molecule(-1) s(-1) for CH3CFClO2 over the temperature range of these experiments.