In this paper, the principle of inertia match has been extended from one degree-of-freedom system to multi-degree-of-freedom systems. Based on the concept of maximum acceleration capacity, we have developed a methodology for the determination of gear ratios in geared robotic mechanisms. We have shown that at the optimum design, the mass inertia matrix of the input links reflected at the joint-space is equal to that of the major links, and the maximum acceleration capacity is independent of the gear train arrangement. Several two degree-of-freedom geared robotic mechanisms have been used as design examples to illustrated the principle. Using this methodology, mechanisms can be designed to yield optimum dynamic performance.