The general equations corresponding to the application of a programmed current of the form I(t)=I(0)t(omega), omega greater than or equal to-1/2 to microhemispheres by supposing different values for the diffusion coefficients of the electroactive couple are presented. When omega=-1/2, it is not possible to reach a transition time under any circumstance. For a reversible process, an independent of time potential is obtained in planar diffusion. This situation is identical to that of chronoamperometry in the same conditions. For usual spherical electrodes the potential depends on time and on root D-i/r(0), and it only becomes dependent on time for microhemispheres for a fixed value of I-0/i(d)(infinity), i(d)(infinity) being the steady-state diffusion current for a microhemisphere. On the contrary, for a current step (omega=0) the potential becomes independent of time at microhemispheres independently of the reversibility of the process. We also analyse the influence of the exponent omega on the potential-time response. Moreover, diagnostic criteria for distinguishing between reversible and irreversible processes and methods for calculating the formal standard potential E-0 and kinetic parameters of the charge transfer are proposed.