This memorandum summarizes information on refractory materials and composites that was presented at the Twelfth Meeting of the Refractory Composites Working Group in Denver, Colorado, on October 17-19, 1966. The memorandum is based on 38 papers that were presented at the meeting. They are reviewed and discussed briefly within the framework of the following four broad areas: materials technology, process technology, specific hardware applications and tests, and evaluation techniques. Included in the section on materials technology are discussions dealing with bulk refractory materials, coated systems, and fiber-reinforced composites. The section on process technology discusses cladding and general fabrication processes. The specific hardware applications and tests cover rocket-motor components, and jet-engine components. The section on evaluation techniques cover thermal, rain erosion, and wear testing. (Author).