ESDU 94021 gives data for all four monohalomethanes, 6 dihalo-, 11 trihalo-, and 11 tetrahalomethanes together with four azeotropic mixtures. Experimental results drawn from the literature for each compound were fitted with a four-term polynomial equation in reduced temperature. The coefficients were also faired with changing molecular structure to ensure the best correlation not only for the individual compounds but also as members of their chemical series. The coefficient correlations also allowed values to be predicted for compounds for which no measured data exist. The equations were used to tabulate thermal conductivity values from the melting point to about 0.9 critical temperature in SI units at 10 K and 10 degree Celsius intervals. The critical point, coefficients and sources of the data are given for each compound. Conversion factors are provided for common British units, the effect of pressure is briefly considered and the likely accuracy of the tabulated values is discussed.