The electrochemical reductive desorption and oxidative readsorption of a self-assembled monolayer (SAM) of dodecanethiol (C12SH) in an alkaline solution were investigated using a rotating gold ring-gold disk electrode. Dodecanethiolate (C12S-), which was reductiveily desorbed from the C12SH SAM modified gold disk electrode, was detected by the gold ring electrode which was kept at a potential where the oxidative readsorption took place. As the rotation rate was increased, the cathodic peak potential for the reduction of the SAM at the disk electrode became more positive and the full width at half maximum of the anodic peak for the oxidative readsorption at the ring electrode decreased. These results suggest that reductively produced C12S- tends to remain on the electrode surface and might form a molecular assembly such as a micelle on the disk electrode surface, thus preventing the residual C12SH SAM from desorbing.