Passive fluid viscous damping systems are generally well suited to vibration control of civil stroctures subjected to seismic excitation. In particular, fluid viscous dampera that operate on the principle of fluid orificing exhibit extraordinarily high levels of energy dissipation density. Such dampers are the primary focus of this paper. The dynamic behavior of a fluid orificing damper is examined through steady-state cyclic test data. Mathematical models of the damper are derived from the cyclic test data and subsequently used in obtaining analytical predictions of the seismic response of II scale-model building structure subjected to earthquake ground acceleration. The discussion on fluid orificing dampera is expanded by considering a generalized mathematical model for describing both linear and nonlinear fluid viscous damper behavior. The energy dissipatiort characteristics of generalized fluid viscous dampers are then examined with reference to the performance of an idealized single-story structure. Finally, a discussion of current applications of fluid viscous dampers for seismic protection of building and bridge structures is presented.