Copper co-deposits underpotentially onto the remaining free platinum sites of Pt(111) and Pt(100) electrodes irreversibly modified with bismuth. On Pt(111), three copper atoms can adsorb on the surface for every bismuth atom displaced, so that no copper can be deposited when the bismuth coverage is 0.33. At slow potential scan rates (2 mV/s), the redox processes associated with the bismuth adlayer and the copper deposition and stripping processes occur at similar potentials around +0.37 V. However, at Easter sweep rates (e.g., 25 mV/s), these processes separate based upon the differing kinetic behavior of bismuth and copper, with the latter exhibiting large increases in Delta E-p (ca. 205 mV at a sweep rate of 25 mV/s) because of its slow deposition and shipping kinetics. On Pt(100), there is a 1:1 relation of the number of copper atoms that can adsorb per bismuth atom displaced. The potentials for copper deposition and stripping and oxidation and reduction of adsorbed bismuth differ sufficiently to allow for a clear separation of the two processes, with the bismuth processes occurring at more positive potentials. The adsorption of both chloride and bromide is induced by copper and bismuth within the mixed adlattice on Pt(lll) in separate processes analogous to the cases for Cu/Pt(111) and Bi/Pt(111) alone. On Pt(111), bromide causes the dissolution of the bismuth adlayer by up to 50%, whereas, on Pt(100), both chloride and bromide cause the complete dissolution of the bismuth adlayer.