This project focuses on the reliability evaluation of building systems designed according to the current U.S. specifications. Knowledge obtained from recent analytical and laboratory investigation and from experience on building performance in actual earthquakes will be the basis of this study. Special attention is paid to quantification of the effect uncertainties encountered in loads and system modeling. Performance and safety evaluation of low and medium- rise buildings will be emphasized. The research will lead to development of consistent reliability-based design methodology and to improved procedures for damage controls under seismic or nonseismic loading conditions.