Composite steel box girder bridges have become an effective alternative to more conventional plate girder bridges and concrete girder bridges in North America in the past 25 years. At present a number of innovations taking place in Ontario and elsewhere have the potential of further enhancing the design, durability, constructibility and, by extension, the economics of steel box girder bridges. These innovations include reduction in the number of boxes, posttensioning of the concrete deck, and construction technology. These developments are by no means the end of opportunities to further enhance steel box girder technology. Combinations of steel boxes and concrete boxes, posttensioned decks, single box girder bridges, multiweb and multicell boxes are all design and construction options that have potential. For the evolution of steel box girder bridges to continue, researchers, code writers, and designers must continue to cooperate with owners and agencies to take advantage of current advances in modeling and analysis software, instrumentation and testing technology, and the current trend among designers and researchers to do more full-scale modeling, analysis, and testing of total bridge structures.