Although usually not considered in design applications, the spatial variations of incident seismic wave motions may, under certain conditions, have a profound influence on the response of structures. To investigate these effects, a new methodology has been developed for analyzing the fully three-dimensional dynamic response of structures that: (1) are above the ground, elastic, and have an arbitrary configuration; (2) are supported on any number of rigid foundations of arbitrary shape that rest on the surface of an elastic half-space; and (3) are subjected to input motions from body or surface waves with arbitrary excitation frequencies and angles of incidence. The superstructure is represented using a finite element model; foundation/soil interaction effects are analyzed using a continuum method. This report describes the general methodology and presents an example of its application to the analysis of a simple single-span bridge/soil system subjected to incident SH-waves. The analysis results clearly demonstrate the importance of traveling wave effects and the influence of different angles of incidence on the three-dimensional bridge response characteristics.