A computer model of the discharge behaviour of the Na-FeCl2 cells is presented. The cell comprises a liquid sodium anode and a porous iron/iron chloride cathode impregnated with NaCl-saturated AlCl3:NaCl molten electrolyte. The anode and cathode are separated by a beta"-alumina solid electrolyte. Both cylindrical (inner and outer cathodes) and flat-plate cell geometries can be simulated. Macroscopic porous electrode theory is used. The cathode reaction is considered to be effectively a solid state process, in that the solubilities of FeCl2 and NaCl are not taken into account. The model predictions show good correspondence with experimental data. The results provide useful insight into cell performance in general and the detailed performance of the cathode in particular.