The thermal bimolecular rate coefficients, O + CH2Cl2 and O + CHCl3, have been investigated in this work over the respective temperature ranges 468-1355 and 499-1090 K using two entirely different techniques. The first technique, HTP (high-temperature photochemistry) at Rensselaer, provided results for the lower temperatures of these ranges, while the higher temperature measurements were carried out at Argonne using the LP-ST (laser photolysis-shock tube) method. Substantial variations in source and reactant molecular concentrations, as well as in other experimental parameters specific to each experiment, were employed in each of the studies. Temperature overlap in the databases was possible with CH2Cl2 but not with CHCl3. The combined results for (1) O + CH2Cl2 --> OH + CHCl2 and (2) O + CHCl3 --> OH + CCl3, are k(1) = 1.1 X 10(-17) (T/K)(1.99) exp(-2855 K/T) and k(2) = 1.9 X 10(-11) (T/K)(0.22) exp(-4755 K/T) cm(3) molecule(-1) s(-1), with estimated 1 sigma accuracy limits of +/-25%. The present results are compared to the related O + CH4 and O + CH3Cl reactions. The four reactions have nearly equal rate coefficients. This is discussed on the basis of BEBO calculations.