Transparent conductors such as indium tin oxide (ITO) are used in a range of optoelectronic devices. Such materials provide both the electrical interface with the semiconductor and a transparent window for the injection or extraction of photons. In AlGaInP surface emitting LED device structures, a particular problem is that of providing an efficient current spreading layer in order to ensure that electrons are injected across the whole of the active region. In this way, the light extracted can be maximised as it originates from the region below the transparent conductor rather than the contact metal. This paper describes a Monte Carlo simulation that can assist in the optimisation of current spreading and light transmission of ITO layers in LED devices. (c) 2007 Elsevier B.V. All rights reserved.