Formosan subterranean termites infesting railway bridge structures were investigated in coastal regions of Texas. Specific sites of the bridges were consistently found to be infested in the non-destructive detection process and confirmed in bridge structures that were partially or totally demolished in the repair or replacement process. Non-destructive detection of Formosan subterranean termite infestations was accomplished utilizing Termatrac radar equipment, acoustic emission detectors, and infrared cameras. Formosan subterranean termites were distributed in the bridge elements, in descending order of concentration, in stringers, piles, and backwalls, respectively. These results can be used to focus inspections of timber railway bridges in maintenance programs and for modification efforts to prevent future infestations of foraging and swarming termites.