We have recently demonstrated that the colon possesses at least 4 pacemakers which presumably generate electric waves and that colonic pacing evokes electric activity in colonic inertia. We tested the hypothesis that electric waves produced by artificial colonic pacing in colonic inertia patients may initiate colonic motilitiy and effect evacuation. 17 patients with constipation due to total colonic inertia were divided into 2 groups: 10 (age 45.6 ± 6.3 years, 7 women) in the study group and 7 (age 43.7 ± 5.8 years, 5 women) as controls. 7 healthy volunteers were included in the study. Colonic pacing was tested at 2 sites of pacemakers: mid-transverse colon and colosigmoid junction. A stimulating electrode was hooked to the colonic mucosa at the pacemaker site and 2-3 recording electrodes distally to it. Healthy volunteers showed resting electric waves in the form of pacesetter and action potentials which increased significantly on colonic pacing. Inertia patients exhibited no basal electric activity. Colonic pacing in the study group evoked electric waves and caused expulsion of small volume balloon. Balloon distension at pacemaker site produced mass movement of balloon, while away from pacemaker site step-wise movement. In conclusion, colonic pacing evoked electric waves in colonic inertia patients and effected balloon expulsion. We postulate that the pacemaker generates electric waves which spread along pacemaker branches that are composed of interstitial cells of Cajal and nerve fibers of the enteric nervous plexus and effect colonic mass contraction. Ex-pacemaker stimulation presumably leads to local activation of interstitial cells of Cajal and segmental step-wise contraction.