The effects of the isotopes N-14-N-15 and/or H-D on the structural CsCl reversible arrow NaCl type phase transition temperature of ammonium chloride using (NH4Cl)-N-14,(NH4Cl)-N-15, (ND4Cl)-N-14, and (ND4Cl)-N-15 have been studied by thermal analysis, TG-DTA and DSC. The TG-DTA curves revealed that these ammonium chlorides exhibit an endothermic peak in the range 183.8-197.3 degrees C with a good reproducibility in spite of sublimation. The exact transition temperatures of these four ammonium chlorides during heating and cooling were measured by DSC. The endothermic peak temperature became 0.4 degrees C lower by substituting N-14 With N-15 in (ND4Cl)-N-14, and 2.3 and 8.7 degrees C lower by substituting H with D in (NH4Cl)-N-14 and (NH4Cl)-N-15, respectively, while the temperature became 6 degrees C higher by substituting N-14 With N-15 in (NH4Cl)-N-14. The exothermic peak temperature was reduced by 15.7 and 14.4 degrees C by substituting N-14 With N-15 and H with D in (NH4Cl)-N-14, respectively.