Changes in micturition behavior and motoneuron ultrastructure were studied in spinal cats to determine the effects of direct current (DC) electric field treatment. Adult cats received a complete injury at T8. A treatment group with an implanted 15 microA DC source and electrodes positioned near the lesion site was compared with non-treatment groups that were either operated or unoperated. Both bladder emptying with Crede and the withdrawal reflex were improved in the treatment group compared with the non-treatment group. Urodynamic procedures showed that high urethral resistance and pelvic floor activity following spinal injury was partially reduced in the stimulated cat, indicating inhibition of the urethral sphincter. The ultrastructural analysis of Onuf's nucleus suggested a similar synaptic input in all three groups. In conclusion, possible activation of inhibitory processes and/or neural plasticity best explain the early improvement of bladder function seen following electrical stimulation.