The hydrogen permeance of several 0.1 mm thick Pd-Cu alloy foils (80 wt.% Pd-20 wt.% Cu, 60 wt.% Pd-40 wt.% Cu and 53 wt.% Pd-47 wt.% Cu) was evaluated using transient flux measurements at temperatures ranging from 603 to 1123 K and pressures up to 620 kPa both in the presence and absence of 1000 ppm H2S. Sulfur resistance, as evidenced by no significant change in permeance, was correlated with the temperatures associated with the face-centered-cubic crystalline structure for the alloys in this study. The permeance of the body-centered cubic phase, however, was up to two orders of magnitude lower when exposed to H2S. A smooth transition from sulfur poisoning to sulfur resistance with increasing temperature was correlated with the alloy transition from a body-centered-cubic structure to a face-centered-cubic structure. (C) 2004 Elsevier B.V. All rights reserved.