The underpotential deposition (UPD) of Bi on Au(110) was investigated in HClO4 solution using in situ scanning tunneling microscopy. The UPD of Bi occurred in three steps. A [Graphics] structure, in which Bi atoms formed dimers, was found for the first UPD adlayer. A (1 x 1) image was obtained by STM at the second UPD peak. For the third UPD peak, Bi atoms formed an incommensurate adlayer, and stripes of Bi were observed on terraces. After the third UPD, a structural reconstruction caused by adsorbed Bi was observed. (c) 2005 Published by Elsevier Ltd.