The adsorption of 2,2'-bipyridine and 4,4'-bipyridine at a gold polycrystalline electrode surface in 0.1 M NaClO4 electrolyte has been studied by electrochemical quartz crystal microbalance (EQCM). The underpotential deposition (upd) process of Pb has been used to understand the adsorption and reorientation of 2,2'-bipyridine and 4,4'-bipyridine. The influence of these two bipyridine compounds on the Pb upd process in 0.1 M NaClO4 electrolyte showed that 4,4'-bipyridine adsorption on Au is surface site selective and both 4,4' and 2,2' bipyridines adsorbate surface structure are potential dependant.