Over the temperature range examined (350 to 475 deg C) polyether-polyurethane rubbers gasify more readily than polyisobutene which, in turn, gasifies at a faster rate than polyester-polyurethane rubbers. Prepolymers gasify at a slower rate than the corresponding polyurethane rubbers. At 350 deg C all of the polymers examined give first order reactions but increasing the temperature to 475 deg C produces deviation from first order behavior. There is evidence that at the higher temperatures free-radical breakdown is responsible for the rapid rate of gas production. Polyisobutene gives a high monomer yield at lower temperatures but at 475 deg C methane and ethylene are also formed. The polyurethane rubbers produce acetaldehyde, methane, ethylene, and carbon monoxide; the polyethers, in addition, give propylene and the polyesters carbon dioxide. Not all of the polymer pyrolysed can be accounted for by these simple gases; the other products probably consist of a mixture of higher molecular weight hydrocarbons.