Supplemental damping (energy dissipation) hardware are being employed in the United States to provide enhanced protection for new and retrofit building and bridge construction. Such hardware includes displacement- and velocity-dependent dampers. The types of dampers being implemented in the United States at this time are presented in the paper. Guidelines and commentary to aid in the implementation of passive supplemental dampers in existing construction are included in the new resource documents FEMA 273 and 274: Guidelines for the Seismic Rehabilitation of Buildings (FEMAThi, 1997). This paper introduces the FEMA 273 analysis procedures and outlines the modeling and analysis procedures developed for implementing supplemental dampers. Two new developments in the field of supplemental damping that will facilitate their application to stiff structural framing systems are the toogle-brace and scissors-jack damper configurations. These configurations are presented in the paper and their utility is demonstrated by comparison with conventional configurations for a sample single-story, single-bay frame.