The electrochemical oxidation of Pt has regained new interest in recent years, motivated by its importance for Pt electrocatalyst stability. New experimental data obtained by in situ methods, detailed electrochemical studies, and complementary results from ab initio theory- and gas-phase studies have led to significant advances in the understanding of this process on the atomic scale. Here, an overview of recent work on the electrooxidation of Pt(111) single crystals in acidic electrolytes, primarily perchloric acid solution, will be given. The complex potential- and time-dependent changes in the adsorbate layer on the electrode surface, the place exchange of oxygen species with Pt surface atoms, the formation of an ultrathin Pt oxide layer, and the structural changes of the electrode surface structure upon oxidation/reduction cycles will be described.