Objectives:Assuming that the characteristic of meridian system has been similar to that of electric potentials in human body and that measurements of electric potential at well(井穴) and sea(合穴) points in branches of the twelve meridians(WSBTM) will be representative of measurements of the twelve meridians, to measure the electric potentials of 17 patients with loin lesions, and pain of loin and lower extremities (腰脚痛, LWLE), to find out the characteristic of meridian system in patients with loin lesions. Methods:Electric potentials of well and sea points in the meridians in 17 patients with LWLE diagnosed by both CT or MRI and self view on pain at loin and lower extremities were repeatedly measured by physiograph(PowerLab). Measurements of those electrical potentials were analyzed by factor analysis. Results The electric potentials of WSBTM at the left side were divided into four factors. On the other hand those at the right side wert divided into three factors.