The finite difference method in conjunction with a conformal mapping technique is used to simulate the diffusion limiting current for three different CE mechanisms at a microdisc electrode. Working surfaces are presented for the variation of the limiting current with a normalised homogeneous kinetic parameter and equilibrium constant. Empirical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. (C) 2007 Elsevier B.V. All rights reserved.