The method we proposed in our previous paper (J. Am. Chem. Soc. 124 (2002) 654) for the construction of mixed monolayers on Au(111) was applied to polycrystalline Au. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and reductive desorption voltammetry demonstrate that the surface coverage of mercaptopropionic acid (MPA) in mixed monolayers with alkanethiol was controlled by the initial coverage of Pb underpotentially deposited during the first step of the preparation. In addition, MPA and alkanethiol did not form single-component domains, the sizes of which are large enough to create two distinct sets of reductive desorption waves. In contrast, single-component domains were formed when mixed monolayers were formed from mixed solutions.