Tendons have been widely used for power transmission in the field of anthropomorphic manipulating systems. This paper deals with the identification and enumeration of the kinematic structure of tendon-driven robotic mechanisms. The structural isomorphism of tendon-driven manipulators is defined and the structural characteristics of such mechanical systems are described. Applying these structural characteristics, a methodology for the enumeration of tendon-driven robotic mechanisms has been developed. Mechanism structures with up to six degrees of freedom have been enumerated.