The underpotential deposition (UPD) of lithium on a polycrystalline gold electrode from poly(ethylene oxide) (PEO)/LiClO4 electrolytes has been investigated both in ultrahigh vacuum (UHV) and in an inert gas atmosphere at ambient pressure, The results obtained at temperatures in the range 55-80 degrees C indicate, as found in earlier studies, that the exposure of a gasket-free, sandwich-type cell to UHV does not affect the overall electrochemical response of the interface observed in more conventional environments. In addition, the voltammetric curves for Li UPD were found to be similar to those reported in Liquid nonaqueous solvent electrolytes, displaying in each case deposition and stripping peaks with areas corresponding to a charge equivalent to the full discharge of a single Li+ per surface site.