Since 1992, the Federal Highway Administration has had a major concentrated research project in the area of horizontally curved steel bridges, the objective of which is to conduct research to better define the fundamental behavior of such bridges. The project involves theoretical work leading to the development of refined predictor equations and verification of those equations through linear and nonlinear analysis and experimental testing of I-girder components. The overall experimental program involves testing of a series of full-scale bending and shear curved steel I-girder components and subsequently a full-size bridge. The development and refinement of predictor equations are summarized, and the work leading to the first series of experimental tests, which involve testing of full-scale bending components, is described.