For the past ten years my research group has been interested in preparing polymeric materials that would retain useful properties as films, fibers, rubbers, or plastics at temperatures of 500°C or more. The program has been sponsored by the Materials Laboratory of the Wright Air Development Division, Wright-Patterson Air Force Base. Our early search for heat-stable polymers was in the field of metal chelates, because some of the monomeric materials of this type seemed to show unusual stability at elevated temperatures. We were never able, however, to obtain truly high-molecularweight polymers that had as good tensile property, modulus, and elongation as were needed for useful structural materials. Moreover, the stability of the low polymers that we did obtain was never quite as good as we had hoped for.