The increasing demands of the military for improved performance of structural materials for space, land, and deep ocean environments has resulted in an intensive activity in the development, evaluation, and prototype testing of a broad range of materials including oxides, carbides, aluminum, titanium, and even gold. A significant portion of this activity has been devoted to high-strength steels. Recognizing the scope of this activity and the need to assemble into one seminar the more recent advances in the development and application of high-strength steels, the Panel on Structural Materials for Airframes and Missiles of the Joint Committee of ASTM and ASME, and the Structural Materials Committee of the Institute of Metals Division of the Metallurgical Society of AIME, organized this Symposium on Steels With Yield Strengths Over 200,000 psi. Until recently, steels having yield strengths in excess of 200,000 psi were not considered suitable as materials of construction, because fabrication and inspection techniques were not sufficiently sophisticated to permit full utilization of these high strengths, which at that time were accompanied by low ductility and low toughness. Recently, however, major developments have occurred not only in alloy development, which has permitted the achievement of higher levels of ductility and toughness, but also in inspection and fabrication techniques that permit the full utilization of higher strengths that are now obtainable. The papers presented at this symposium included descriptions of new steels (or new concepts for making steels) having yield strengths in excess of 200,000 psi, and good ductility and toughness. Specifically mentioned are the new maraging steels, higher strength and higher toughness martensitic steels, steels strengthened by thermomechanical treatments, and steels strengthened by cryogenic treatments. Progress has been made in the understanding of the illusive property known as toughness, and two papers are presented summarizing the state of art in this area. Also the effect of melting and processing on high strength properties, the characteristics of specific products—namely, forgings and fasteners—and the fabrication of the new high-strength steels are discussed in detail.