The treatment of the irritable bowel syndrome (IBS) is not entirely satisfactory as the exact cause of the condition has not been revealed. We have demonstrated in a recent study that the IBS exhibited a "tachyarrhythmic" electromyographic pattern; the wave rhythm was irregular and wave variables were higher than those of the healthy volunteers. We suggested that a disorder of the colonic pacemaker discharges these abnormal waves thereby causing the motor disorders of IBS. In another study, we determined the colonic pacing parameters needed to modulate the disordered pacemaker. In the current communication we investigated the effect of colonic pacing, using these parameters, on the EMG activity of the sigmoid colon (SC) and on the clinical manifestations of patients with IBS. A pacemaker was implanted in a subcutaneous pocket in the inguinal area and its two leads were hooked to the colosigmoid junction. The effect of colonic pacing on the SC EMG activity was investigated by inserting two recording electrodes into the SC muscle. The patients were then trained for home pacing after removal of the 2 recording electrodes. Nine patients (age 42.7 +/- 4.2 years, 6 women) with IBS were studied. The pre-pacing tachyarrhythmic pattern of EMG was recorded. On colonic pacing, the slow wave rhythm became regular and wave variables were normalized; the symptoms of the IBS improved. The optimal parameters used for pacing comprised an amplitude of 6 mA, a pulse width of 150 ms and a frequency of 25% higher than that of the basal colonic waves. In 7/9 patients the improvement of symptoms continued when pacing was ceased after 6 months of daily pacing; the pacemaker was removed after 3 months of non-pacing. In 2/9 patients, pacing needed to be continued because the symptoms recurred each time the pacing was ceased. In conclusion, colonic pacing succeeded in normalizing the tachyarrhythmic pattern and relieving the symptoms of the IBS. No complications were encountered and the method was well accepted and tolerated. Further studies on a large group of patients are required.