Chronoamperometry has been used to study the reduction of aliphatic thiols chemisorbed on a Au(111) single crystal electrode in 0.1 M KOH. The chronoamperograms of the reductive removal of butanethiol and nonanethiol monolayers are relatively symmetric when the value of the final potential is not too negative. For more negative final potentials and for a hexadecanethiol monolayer, the chronoamperograms are asymmetric with a fast rising edge and a slow decay. We analyzed the chronoamperometric data with a nucleation and growth model in which the reductive removal of a thiol monolayer starts by the creation of etching centers and continues with the reduction of the thiols that are at the edge of the etching centers. For the least negative final potentials, the short chain thiols (butanethiol and nonanethiol) are found to desorb reductively from a limited number of etching centers. However, for the more negative final potentials and for the hexadecanethiol monolayer, the reductive removal occurs homogeneously across the electrode surface instead of only at a few etching centers.