The bismuth UPD was studied on Au(1 1 1) electrodes modified by silver intermediates and adsorbed thymine. Cyclic voltammetry, potential step experiments and X-ray photoelectron spectroscopy were used for investigation. The results were compared to the results of the analogous experiments performed on bare Au(1 1 1) and on bulk silver. In the first part it is shown that the Bi UPD on Ag(ML)/Au(1 1 1) differs completely from the UPD on Au(1 1 1) as well as on bulk Ag due to changed electronic properties of the substrate. The 2nd part focuses on the Bi UPD in presence of the nucleobase thymine. Thymine undergoes a reorientation from the chemisorbed state to the physisorbed state on Au(1 1 1) at potentials where the Bi UPD takes place. During the UPD adsorbed thymine is replaced by Bi species on the electrode surface. It does not re-adsorb on top of the deposited Bi layer. An energetic advantage due to re-adsorption on topmost layer as described for the Cu UPD on thymine modified Au(1 1 1) does not occur. (c) 2009 Elsevier B.V. All rights reserved.