The purpose of this investigation is to determine the effect on the temperatures and the performance parameters of the addition of (1), liquid hydrogen, and (2), liquid ammonia to three bipropellant systems currently of interest. These bipropellant systems are: nitrogen tetroxide-hydrazine, hydrogen peroxide-hydrazine, and RFNA-hydrazine. For each of the six tripropeliant systems investigated the chamber temperature, exhaust temperature, and all the important parameters were calculated. These calculations for each system were carried out for both equilibrium flow and constant composition flow assumptions. All the results are listed in tables and the more important parameters are presented in graphical form as well. One hydrogen containing system and one ammonia containing system are discussed in detail. General results for all systems include the fact that the largest proportionate decreases are observed in the variation of the exhaust and chamber temperatures whereas the specific impulse shows slight increases or proportionate decreases of much smaller magnitude than the proportionate decreases in temperatures. Several new parameters are introduced in an effort to make possible the prediction of performances of a tripropellant system if the chamber temperature variation is known. These parameters may also be used in an indirect manner to illustrate the relative merit of liquid hydrogen and liquid ammonia as coolants in tripropellant systems.