The effects of sennosides (Sen, an extract of Chinese rhubarb) on cellular spontaneous electric activities of guinea pig taenia coli were studied by intracellular microelectrode technique. Sen 0.1-20 mmol.L-1 improved the depolarization of cell membrane, quickened the burst of slow wave potential, and increased notably the frequency of spike potentials. Sen (20 mmol.L-1) induced spontaneous spike potentials. These results provide direct evidence for the enhancing effect of Sen on intestinal peristalsis at cellular level.