Considerable attention has been paid to passive and active structural control research in recent years, with particular emphasis on alleviation of wind and seismic response. Passive control systems encompass a range of materials and devices for enhancing damping stiffness and strength, and can be used for both natural hazard mitigation and for rehabilitation of aging or deficient structures. In recent years, serious efforts have been undertaken to develop the concept of energy dissipation, or supplemental damping, into a workable technology. Active systems and some combinations of passive and active systems, so-called hybrid systems, are force delivery devices integrated with real time processing evaluators/controllers and sensors within the structure. Remarkable progress has been made in both areas of research and implementation. This paper provides an assessment of the state-or the-art and state-of-the-practice of structural control technology. The focus is on passive supplemental energy dissipation technology.