The long-range diffusion of deuterium in tantalum has been investigated as a function of temperature by means of the anelastic process due to redistribution of deuterium impurities between compressed and dilated regions of the sample, under an applied stress alternating at about 4 Hz. The diffusion coefficient was found to obey an Arrhenius-type law in the temperature range 200–390 K; a deviation was observed at lower temperatures. The diffusion parameters in the exponential region areD 0D=(3.3±1.5)×10−4 cm2/s, andW D=(0.176±0.008) eV.