In order to properly interpret the thermal conductivity of molten silicate slags, several different measurement methods are briefly reviewed, along with a discussion as to their respective advantages and limitations. In addition, a large number of thermal conductivity values measured by these methods are assessed, in order to evaluate their dependence on composition and temperature. The behavior of the thermal conductivity of molten silicate slags was found to show good agreement with well-focused analyses into its microstructure. Moreover, with an improved understanding of the microstructure of silicate slags, there is an apparent co-relation between thermophysical properties such as thermal conductivity, viscosity, and so forth.