Continued increases in the speed of tactical systems have forced current ceramic radome materials to perform near their operational limits for thermal stresses. In addition, the all-weather requirements for emerging systems and the potential for erosion and fracture from particle impacts have necessitated the development of improved radome materials for these environments. Among the concepts being developed for these applications is a class of reinforced ablative materials which consist of polytetrafluoroethylene (PTFE) filled with borosilicate or glass in either particulate or microfiber form. RT/duroid is a material of this class and has attractive thermal and electrical properties. However, an accurate definition of the ablation-erosion and thermal performance of materials is required since transmission characteristics are sensitive to radome thickness and temperature.This paper reports the results of a combined experimental-analytical program that was conducted to define the thermal-ablation and erosion performance of RT/duroid 5870M, a candidate ablative radome material. The resultant thermal-ablation model is demonstrated to provide excellent predictions of thermochemical ablation and in-depth thermal response. The shape change of RT/duroid 5870M models in the clear air and rain environments of Holloman Mach 5 sled tests is also well predicted by a computer code that uses the ablation model and an erosion model based on work by Letson and Schmitt.