The electrochemical behaviour of Ir(1 1 1) electrodes has been studied in simple aqueous solutions, in the presence and absence of various adsorbates: sulphate, phosphate and halide anions. In general, this electrode is very similar to Pt(1 1 1); however, the rates and relative strengths of adsorption are different. In the accessible potential range no capacitance peak similar to that of Pt(1 1 1) was found, and no Gouy-Chapman minimum could be identified. CO adlayer stripping from Ir(1 1 1) in sulphuric acid occurs in the same potential region as for Pt(1 1 1). (C) 2005 Published by Elsevier B.V.