The static characteristics of a two-terminal P-N-P-N diode are discussed. Switching of this diode is controlled by varying the applied voltage and current. Majority logic is then considered. Functions can be converted to majority form from Boolean expressions using an axiomatic majority-decision logic majority logic circuits can be analyzed with Karnaugh maps. A three input majority logic circuit using P-N-P-N diodes and passive circuit elements is presented. An analysis of the circuit shows that it is possible to obtain any number of outputs with component tolerances of 5 percent. The operating frequency is less than 200 kc. The circuit is practical for application where high speed is not required and diodes can be obtained at a low cost.