Non-steady-state zone electrophoretic processes can be treated by repeated application of a steady-state mathematical model. Based on this principle, a computer program was set up for the simulation of electropherograms on a temporal basis. Because all parameters of the sample zones can be calculated, all possible detector traces can be simulated. Simulated electropherograms were compared with experimentally determined electropherograms to establish the ability of the mathematical model in qualitative respects. It appears that with this model the fronting and tailing character of sample peaks can be predicted and the reversal of the fronting/tailing character at the point where the mobility of the sample ions equals that of the co-ions. It was remarkable that for strong sample ionic species and applying weak co-ions, the originally tailing character did not change into a fronting character when the mobility of the sample ions exceeded that of the co-ions. Also, the appearance of peaks and dips for the distinguished cases in indirect and direct UV detection can be predicted by the model.