Pt/Au thin‐film couples were heat treated in 1 atm N2, He, and in vacuum. The outdiffusion kinetics of Au through the Pt were determined by measuring the Au concentration on the Pt surface using Auger electron spectroscopy. Au was found to outdiffuse through 6–10 kA˚ Pt at rates 15 and 30 times faster in 1 atm N2and 1 atm He, respectively, than in vacuum, at 350 °C. These results are the first published documentation of the remarkable acceleration of thin‐film interdiffusion caused by the presence of nonreacting gases.