The application of the high-speed channel microband electrode to potential step transient measurements is reported. Potential step experiments, from conditions of no current flows up to a potential value where the mass transport limited current is reached, using the one-electron oxidation of N,N,N’,N’-tetramethyl-1,4-phenylendiamine and the one-electron reduction of p-bromonitrobenzene and p-chloronitrobenzene are reported. The applicability of a model in which the dominant mass transport form is by diffusion normal to the electrode and by convection axially through the channel is demonstrated so that axial diffusion effects are negligible. This permits the use of the backward implicit procedure to analyze the experimental transient responses incorporating any kinetic complications, as appropriate. It is shown that homogeneous rate constants of at least 1 order of magnitude higher are accessible by potential step transient measurements for an ECE mechanism as compared to steady-state experiments.