The permeation of hydrogen through metal membranes can be strongly affected by surface impurities for conditions where surface processes dominate over bulk diffusion. Hydrogen permeation was measured in both the surface-limited and diffusion-limited regimes between 300 and 700 K using a membrane technique. Molecular hydrogen (1×10−3–3×104 Pa) was used to determine the membrane permeability and the overall surface-limited permeation rate constant. Atomic hydrogen (3×1015–2×1019 H0/m2 s) incident on either side of the membrane was used to determine the contribution of each surface to the overall surface-limited permeation rate. Impurity concentration on one of the membrane surfaces was monitored in situ with an Auger electron spectrometer. This same surface could also be sputter-cleaned by argon ions. Removal of surface carbon, oxygen, and sulphur had no measurable effect on the diffusion-limited permeation, but increased the surface-limited permeation rate constant by orders of magnitude.