Computer-assisted procedures for the one-parameter optimization of the surfactant concentration and the concentration of urea or D-glucose as modifiers in micellar electrokinetic capillary chromatography have been developed. These procedures permit a rapid optimization of one parameter on the basis of only two experiments. Predicted values are compared to empirically obtained optimum values. The influence of the modifier concentration on the critical micelle concentration of sodium dodecyl sulfate was experimentally determined in buffers commonly employed in micellar electrokinetic chromatography. The alteration of retention factors of solutes caused by the influence of urea addition on the critical micelle concentration of sodium dodecyl sulfate was calculated under the assumption of constant distribution coefficients and compared to experimentally obtained values. It was demonstrated that the addition of urea or of D-glucose does not alter the phase ratio substantially.