The Third Conference on Composite Materials: Testing and Design was held 21-22 March 1973 in Williamsburg, Va. Committee D30 on High Modulus Fibers and Their Composites of the American Society for Testing and Materials sponsored the conference in conjunction with the Metallurgical Society of the American Institute of Mining, Metallurgical, and Petroleum Engineers and the American Society of Mechanical Engineers. C. A. Berg, University of Pittsburgh, F. J. McGarry, Massachusetts Institute of Technology, and S. Y. Elliott, Douglas Aircraft Company, served as coordinators. Most of the papers presented at the eight sessions are included in the volume which complements the first and second conference publications, ASTM STP 460 and ASTM STP 497, Composite Materials: Testing and Design.