Reaction between Ti metal and B 2 O 3 is investigated using x-ray photoelectron spectroscopy, scanning electron microscopy and wavelength dispersive spectrometry mapping techniques because titanium-to-borate glass seals have great potential for use in biomedical and aerospace applications. Immediately after the deposition of a 3 nm thick titanium film under UHV conditions on in situ fractured B 2 O 3 at room temperature, TiB x , Ti-O-B and Ti-O-Ti linkages are formed. The following initial reaction occurs at the Ti-B 2 O 3 interface Ti+xB 2 O 3 →TiB 2x-2 +B 2 O 3-y +1/2(y+3x-3)O 2 . In situ heating of the film leads to the incorporation of released oxygen in both the product TiB x layer and the titanium film. TiB x precipitates are formed on the titanium side of diffusion couples prepared at 1000°C. The implications of these results for glass-to-metal adherence are discussed.