In recent years, considerable attention has been paid to research and development of structural control devices, with particular em-phasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken in the last two decades to develop the structural control concept into a workable technology. Full-scale implementation of active con-trol systems have been accomplished in several structures, mainly in Japan; however, cost effectiveness and reliability consider-ations have limited their wide spread acceptance. Because of their mechanical simplicity, low power requirements, and large, con-trollable force capacity, semiactive systems provide an attractive alternative to active and hybrid control systems for structural vi-bration reduction. In this paper we review the recent and rapid developments in semiactive structural control and its implemen-tation in full-scale structures.