To ensure structural safety in a devastating earthquake, positive use of nonlinear characteristics on a structure is more effective than simply examining nonlinear behavior on it. This idea provides us with structural control and can be realized as a result of integrating various fields of technologies. Then, we must promote both academic research and practical development, which stimulate each other and bear two-wheel intertwining fruits. Prof. Caughey understood it well and left a bunch of achievements and contributions on both aspects as signs towards our final goal. Copyright (c) 2005 John Wiley & Sons, Ltd.