In one technique, a desired electrical current distribution on at least three active electrodes is selected. An electrical energy perturbation is generated on at least one electrode. A current-to-voltage relationship at each active electrode is estimated based on the energy perturbation. The current-to-voltage relationship for each active electrode takes into account current flow through other active electrodes. The voltage distribution necessary to achieve the desired current distribution is determined based on the estimated current-to-voltage relationship. Voltage-regulated energy is conveyed between the electrodes and tissue in accordance with the determined electrical voltage distribution. In another technique, an electrical energy perturbation on at least one of the electrodes is generated. Network resistances for each of at least three active electrodes are computed in response to the energy perturbation. The network resistances represent the resistances between the electrodes and common node to which the electrodes are connected.