Oxygen exchange experiments have been performed between single crystals of sanidine feldspar and oxygen gas enriched in 18O, at temperatures in the range 869-1053°C, total pressure 1 atmosphere, for times up to 28 days. Oxygen isotope diffusion profiles in a direction perpendicular to (001) were determined with an ion microprobe. The experimental data obey a single Arrhenius relationship of the form D = 8.4 × 10-11 exp. (-245 ± 15 kJ mol-1/RT) m2s-1. The results indicate that oxygen diffusion in anhydrous sanidine feldspar is marginally slower than oxygen diffusion in anhydrous anorthite. Comparison with published atomistic simulation studies suggests that oxygen transport in feldspar is by an interstitial mechanism.