The Proceedings contain the papers presented at the Thirteenth Symposium on Optical Materials for High Power Lasers held at the National Bureau of Standards (NBS) in Boulder, Colorado, on November 17–18, 1981. The Symposium was jointly sponsored by the National Bureau of Standards, the American Society for Testing and Materials, the Office of Naval Research, the Defense Advanced Research Projects Agency, the Department of Energy, and the Air Force Office of Scientific Research. The Symposium was attended by approximately 200 scientists from the United States, the United Kingdom, Japan, France, West Germany, the Peoples Republic of China, Sweden, and the USSR. It was divided into sessions devoted to the following topics: Materials and Measurements, Mirrors and Surfaces, Thin Films, and finally Fundamental Mechanisms. The Symposium Co-Chairmen were Dr. Harold E. Bennett of the Naval Weapons Center, Dr. Arthur H. Guenther of the Air Force Weapons Laboratory, Dr. David Milam of the Lawrence Livermore National Laboratory, and Dr. Brian E. Newnam of the Los Alamos National Laboratory. They also served as editors of this report. Dr. Alexander J. Glass of KMS Fusion acts as Conference Treasurer with Aaron A. Sanders of the National Bureau of Standards as the Conference Coordinator.