Measurements were made of heat generation in aluminium electrolytic capacitor ’sandwiches’ operating under pulse charge and discharge. With commercial anode foils the fraction of input power dissipated as heat in the dielectric is proportional to the DF of the oxide dielectric. There is also a dependence on the applied voltage that is thought to be due to frictional losses arising from expansion and relaxation of the oxide in the pulsed field. This field dependence is specific to the commercial etched aluminium foils and is absent when the oxide dielectric is grown on smooth substrate, indicating a dependence of the stresses in the oxide on the etch structure. The oxide degrades under isothermal pulse operation at 60 degrees C, with both DF and heat generation increasing proportionally. Oxide ’reformation’ brings these properties back to their initial values, or lower, and stabilizes the dielectric during subsequent pulse operation. An amorphous anodic oxide dielectric deposited at room temperature on commercial etched foils had different characteristics. The fractional heat dissipation was equal to the lowest observed with the commercial oxides, but was independent of oxide DF. Long term isothermal pulsing produced only slight degradation of the oxide properties.