The rapid development that has occurred in seismic codes has left a need to review the theoretical framework underlying the process of modern seismic design, to make it more accessible and to explain its logic to those outside the small circle of experts. The design guide aims to satisfy this need by outlining and comparing the approaches taken by regional codes (New Zealand, USA, Europe and Japan). Next follows a chapter on reliability-based system analysis that demonstrates that the problem of seismic design can be theoretically formulated in a comprehensive way that can provide results of practical value. The main part of the guide is devoted to practical issues relating to the measurement of seismic performance and case reports. The detailed discussions provided will enable the interested reader to understand the relative importance of the numerous parameters involved in seismic design and the relationships between them, as well as the motivations behind the choices adopted by the codes. The final chapter on the assessment of existing buildings covers a crucial topic for the future of earthquake engineering.