This work describes the preparation of nanocrystalline-graphite inlaid ring ultramicroelectrodes (UMEs) with inner diameters larger than 0.31 mu m and thicknesses as low as a few nanometers. The geometric parameters of these UMEs were determined by a combination of optical microscopy and cyclic voltammetry data. These UMEs permit to establish mass-transport rates as large as those obtained on nanometer-sized hemispherical UMEs. They have very low electrochemical activity in acid and can function very well as catalyst supports for kinetic studies of fuel cell reactions such as the hydrogen oxidation reaction (hor). In order to demonstrate the outstanding utility of these electrodes, compact Pt films were electro-deposited on graphite ring UMEs and used to carry out a kinetic study of the hot in acid medium. (C) 2010 Elsevier B.V. All rights reserved.