In this paper the transient solution of a potential step at a rotating disc electrode (ROE) for irreversible and quasireversible one electron transfer reactions is derived by Nernst diffusion layer approximation and separation of variables. This is then compared to finite element simulation results. For the initial conditions steady state concentrations are chosen, such that with this theory it is possible to fit and simulate quasi steady-state linear sweep RDE measurements or other quasi steady-state sequences of potential steps. It was found that it is possible to derive accurate closed form solutions for the initial parts of the transient response. However, the Nernst diffusion layer approximation leads to inaccuracies in the intermediate times with relative errors of up to 10%. By fitting the initial transient to the closed form solution it is possible to extract steady state background currents. Additionally, we use the potential step theory to derive an expression for kinetically controlled transition times and show that these can exceed the mass transport controlled transition time. (C) 2011 Elsevier Ltd. All rights reserved.