Glass-ceramics in the tungsten-titanium-phosphate system were first reported in 1992. The glass-ceramics exhibited electrical resistivity as low as log(rho) = -1.8 omega center dot cm, which was attributed to an interconnecting network of tungsten suboxide crystals, WO3-x. A new identification of the conducting phase as a phosphate tungsten bronze, (PO4)(2)(WO3)(2m), is reported. High-temperature x-ray diffraction and electron microscopy have been used to provide a detailed description of the crystalline phases and their development. As the ceramming temperature was raised, the phase assemblage progressed from cubic tungsten oxide and titanium pyrophosphate to phosphate tungsten bronzes. The m-values of the bronzes ranged from 2 to 7 depending on composition.