Visible electroluminescence (EL) from n-type porous silicon (n-PS) in an electrolyte solution containing S2O82- was investigated by potential-sweep and potential-step methods. Potential sweep measurements showed that both the cathodic current and EL intensity increased and the EL spectra blue-shifted as the potential became negative. These characteristics were further studied by the potential-step method. immediately after the potential was stepped to a negative value, the cathodic current began to flow and EL was observed. The EL intensity then increased but the cathodic current decreased with time. The rate of the increase in the EL intensity depended not on the S2O82- concentrations but on the applied negative potentials. Time-resolved EL spectra measurements showed that the EL spectrum was blue-shifted with time even when a constant negative potential was applied to n-PS. These results were explained by considering that the emission site was changed from larger-sized Si crystallites to smaller-sized ones in the n-PS layer with time.