Ablative polymers and polymeric composites serve an important function in aerospace technology. They protect aerodynamic surfaces, propulsion structures, and ground equipment from degradative effects of very high temperatures or incident heating rates. This protective function is accomplished by a self-regulating heat and mass transfer process known as ablation. By this relatively new process, thermal energy is expended via sacrificial loss of material. The amount of energy absorbed, dissipated, and blocked depends critically upon both materials and environmental variables. including the properties of the polymeric material, the thermal-chemical-mechanical aspects of the environment, and the complex interaction of the ablator with its hyperenvironment. Important thermochemical and thermo-physical parameters of the ablation process are discussed. In addition, a state-of-the-art of polymeric ablators is presented, with emphasis on the advantages, limitations, and current problems associated with ablative plastics. The need for charring, noncharring, inorganic, low-modulus, cryogenic, processible, and low-cost polymers is discussed in considerable detail. Lastly, the service uses developed for ablative polymers during the past decade are reported to illustrate the importance of this new class of engineering materials.