Jing and Luo designate two important types of vessels (Mal) used by Oi to circulate in the whole body : the meridians (Jing) and their collaterals (Luo). the expression Jing Luo is a generic term defining the whole network or circuits of the meridians and their collaterals. the role of the Jing Luo system is to provide intervisceral connections and communication between the viscera and the extremities, and to regulate the function of each part of the body. This system permits understanding and analysis of a great number of symptoms falling into theoretical clinical frameworks (Zheng) and whose manifestation sites cannot be explained otherwise than by the courses of meridians. Working out a combination of points presupposes not only a deeper understanding of the men-i- dians (Jing) but also of their secondary channels (Luo). lf these secondary channels are ignored, then the action of certain points on zones which the main meridian does not touch becomes incomprehensible. As the Jing Luo system is of the utmost importance in diagnosis and therapeutics, it may be considered to be the cornerstone of Chinese medicine.