The influence of segregated sulfur on palladium permeability was investigated using deuterium permeation through palladium membrane, which was pretreated by annealing in vacuum and/or in air. It has been found that the palladium membrane is almost impermeable after vacuum annealing, while it is permeable after air annealing. A combination of vacuum annealing of a Pd membrane followed by annealing in air leads to better and more stable D-2 permeation because S has been depleted from the Pd bulk. In fact, cleaning S from Pd in spell out (UHV) normally proceeds via cycles of high T annealing to drive S to the surface, followed by burning off the S as SO2 by heating in an O-2 environment. The results in this study well demonstrate the influence of sulfur on the deuterium-permeation rate and on the behavior of sulfur segregation from Pd bulk to the surface. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3273318]