The variation of supporting electrolyte concentration so that the relative contribution of migration and diffusion to transport is altered has been shown to be mechanistically revealing in some cases. We consider the following ECE/DISP1 mechanism, in which the chemical step, B (sic) C, is an isomerisation: A + e(-) (sic) B B (sic) C B + C (sic) A + P C + e(-) (sic) P This system is studied by simulating voltammetric responses at a hemispherical microelectrode over a range of scan rates and support ratios. A wide range of rate constants for the intermediate chemical step are investigated. It is found that, for a certain range of rate constants, significant variations become apparent in the responses of the two mechanisms. In particular it is found that for intermediate values of the rate constant of the chemical step, the reductive current produced from an ECE mechanism is reduced relative to that of DISP1 as the support ratio is lowered. (C) 2011 Elsevier B.V. All rights reserved.