The economic consequences and loss of life make earthquake disasters catastrophic anywhere in the world. Seismic retrofitting, or repair, of buildings is an essential component for mitigating the effects of earthquakes. In the last twenty years advances in the various techniques for seismic retrofitting have been made and put into practice. Fastening systems have been used for almost all retrofitted buildings and it is essential that fasteners transfer the repeated seismic actions between new and existing elements. This state-of-the-art report reviews and introduces the latest design concepts and methods for seismic retrofitting throughout the world, with emphasis on the use of fastening systems.