Ablative materials have been used widely by the Navy to protect both the internal and external surfaces of solid-propellant missile propulsion systems. Plastics and rubber-based ablators have been employed for this purpose because of their relatively low density and high thermal insulation performance. To aid in the development and selection of these materials, lab oratory-scale thermal tests have evolved. An oxyacetylene burner test found to be useful for this purpose has gained widespread acceptance and is now a standard procedure known as ASTM 285–65T. Standardization of other test procedures and techniques is in process. These include a method for determining the total enthalpy of electric plasma arc heaters and recommended practices for installing thermocouples in ablative test specimens. An advanced technique in use at the Naval Ordnance Laboratory (NOL) known as the “alpha rod test” provides a continuous record of ablation rate and internal temperature. It also enables one to compute the effective thermal diffusivity as a function of temperature, which is suitable for predicting internal temperature histories in ablators. Under ideal conditions, agreement to within 5–10% of experimental data has been obtained. Using the concept of “constructive thermal degradation,” NOL has also developed new, novel epoxide resin-curing agent systems equal to or better than phenolics in ablation performance.