This collection of nine technical papers discusses the behavior of welded connections in building structures when subjected to strong ground shaking during severe earthquakes. The material presented in the papers is primarily derived from the findings of the FEMA-sponsored research program which focused on the behavior of steel moment frames in the 1994 Northridge earthquake. Topics include: weld fractures observed in moment resisting frame connections; strength issues raised by the fractures and how these properties affect the reliability of the connections; quality assurance during construction; importance of technician competence on ensuring the success of the QA program; methods for nondestructive evaluation of completed welds; and repair strategies and design issues. These papers demonstrate the scale and rigor of attention that is required in design and construction to ensure steel buildings will perform as intended in future earthquakes.