Shot peening introduces subsurface residual compressive stresses in titanium alloys to depths of up to 500 µm. Although the microhardness method is established as a method for determining interstitial oxygen concentration gradients of such alloys, the near surface plastic deformation arising from shot peening is a source of measurement unreliability. An alternative method based on negative ion, focused ion beam–SIMS has been trialed for a shot peened Ti-834 alloy thermally exposed for times and temperatures comparable with service conditions in the ‘hot-end’ compressor stages of a modern gas-turbine aero-engine. Focused ion beam–SIMS measurements successfully measured enhanced oxygen ingress into the topmost 100 µm of the shot-peened Ti-834 after prolonged thermal exposure. Copyright © 2012 John Wiley & Sons, Ltd.