Variable temperature scanning tunneling microscopy (STM) has been used to image oxide-supported nanoclusters of Au at temperatures from 300 to 450 K and oxygen pressures from 10(-10) to 4 Torr. Oxygen-induced morphological changes of the TiO2(1 x 2) reconstruction are apparent at room temperature and prolonged exposure (similar to3 x 10(3) L (langmuir)) at 10(-4) Torr oxygen. Gold clusters with diameters smaller than similar to4 nm are unstable toward sintering at ca. 450 K and oxygen pressures >10(-1) Torr. Oxygen at pressures >10(-4) Torr weakens the interaction between the gold cluster and the titania support. Increasing the sample temperature to >300 K facilitates disruption of the duster-support interaction.