A combination of chemical balancing and thermal-mechanical processing has led to a new class of high strength steels. These steels utilize the strain-induced austenite to martensite transformation to produce unusually good combinations of strength, elongation, toughness, and corrosion resistance. The principle behind enhanced elongation is discussed in terms of the increased work-hardening rate provided by the hard martensitic phase. The mechanism responsible for enhanced toughness is discussed in terms of the plastic energy absorption occurring during the transformation. It is further shown that elongation is three times greater, toughness may be two times greater in thin or thick sections, and corrosion resistance is an order of magnitude greater than the comparable properties of conventional, high-strength martensitic steels.