Simple implementations of quaternary full adders are proposed for a high-performance multi-processor which consists of many processing elements (PEs).Arbitrary quaternary functions are represented by the combination of input-value conversion and several quaternary output generations.The use of appropriate input-value conversion makes it possible to reduce the number of output generators, which improves the performance of the resulting quaternary full adders.For example, two kinds of single PEs including a quaternary full adder and two flip-flops are implemented using the proposed method and their efficiencies are demonstrated in terms of delay and power dissipation in comparison with those of a corresponding binary CMOS implementation.