A new software package is described for 2-Dimensional modelling of microwave heating. It is particularly suited to the high temperature heating of ceramics, where electrical and thermal properties are strongly dependent on temperature. The described program, x_tlm, runs under Xwindows, which allows a microwave cavity and its contents to be entered graphically and stored as a schematic diagram. The diagram is automatically converted into a mesh format for simulation using a topology independent Transmission Line Modelling formulation. Temperature dependencies of material properties are specified as polynomial functions of temperature. Surface heat loss by the radiation mechanism, which dominates at higher temperatures, is also introduced into the model.