It has been demonstrated that supplemental damping can be an effective means for reducing forces and displacements of structures during earthquakes in both the elastic and inelastic ranges of structural response. In prior investigations on the subject the mechanical characteristics of several supplemental damping devices have been established and verified by static and dynamic experiments. The main objective of this project is to establish an engineering basis for identification of supplemental damping characteristics which could provide cost effective improvement in earthquake response performance of buildings above that currently provided by traditional design. This will be accomplished by (1) comparing building cost and earthquake response using supplemental dampers with those using current code designs and (2) assessing the significance of damper distribution throughout the building on performance and consequently on the ease of designing buildings with added damping. Successful research achievement under this project will ensure acceptance of supplemental damping as a viable alternative to traditional designs.