The purpose of the present study was to evaluate the effect of an electronic toothbrush on established plaque and gingivitis in a 5-month clinical trial. This electronic toothbrush sends approximately a 0.15 mA current through the brushhead which presumedly enhances the efficacy of the brush in plaque elimination. For this study, 80 volunteers (non-dental University students) were selected on the basis of having moderate gingival inflammation. At baseline, plaque and bleeding upon probing were assessed on the vestibular, mesio-vestibular, distovestibular and lingual surfaces using the 'half-mouth' design. After 2-months and 5-months, these clinical indices were again recorded. At each assessment, the participants received a new brushhead. All baseline indices appeared to be well-balanced. A mean Silness and Löe plaque score of 1.70 and 1.64 were found in the control and test groups, respectively. Little change was observed from baseline to 5-months. The Quigley and Hein plaque index behaved comparably. The mean bleeding upon probing score at baseline was 1.43 and 1.39 for the control and test group, respectively. Little to no improvement was observed in the course of this study. No beneficial effect could be shown for this 'electronic' design of manual toothbrush.