The report summarizes the advancements made in the development and welding of steels possessing yield strengths greater than 150,000 psi. Steels discussed include the medium carbon, low-alloy martensitic steels; low carbon alloy martensites; and nickel maraging steels. Almost all programs which have the objective of developing high-strength steels have an equally important phase concerned with filler metal development. Filler metals are also discussed. The new welding processes discussed are Narrow-Gap welding, electron-beam welding, plasma-arc welding, high-frequency resistance welding, electroslag welding, laser welding, and interrupted-arc (dip trasfer) MIG welding. (Author).