Abstract A systematic study of the surface morphology of Pt(111) and Pt(100) electrodes as prepared by flame-annealing and cooling in different atmospheres (air, N 2 , H 2 +N 2 and CO+N 2 ) is presented. The electrodes were characterised by cyclic voltammetry and in-situ STM in 0.1 M H 2 SO 4 . Preliminary voltammetric results for Pt(110) are also shown. In this case, Cu upd served as a structure sensitive probe. It was observed that the presence of oxygen during cooling induces surface defects and leads to rough surfaces. Cooling in pure N 2 preserves the reconstructed Pt(100) and Pt(110) surfaces, while cooling in H 2 +N 2 or CO+N 2 lifts the reconstruction. The use of CO as the cooling gas turned out to be advantageous for the preparation of clean and well-ordered (1×1)-surfaces. The stability of reconstructed Pt surfaces in an electrochemical environment is discussed. For H 2 +N 2 -cooled Pt electrodes, a clear influence of the H 2 -concentration on the surface morphology was observed.