Thermal coupling and etch rate measurements are reported for polyethylene terephthalate and polyimide films irradiated at excimer laser wavelengths of 193, 248, and 308 nm. Thermal energy balance is observed up to a threshold fluence but above this the energy absorbed remains approximately constant, the excess energy being carried away by the ablated material. The ablated material appears to have a temperature >103K as determined by calculations based on the thermal energy loading and relaxation time estimated from IR measurements. These results provided useful information on the interaction mechanism.