The catalytically important high-silica zeolites NaSPM, NaLPM and NaY, which had been exchanged with different metal cations, Cu, Ni and Co, were examined through ammonia desorption by differential scanning calorimetry. The acidity of the different zeolite samples was investigated and correlated to the framework and structural alterations following cation exchange. The activation energy values for the different zeolite samples were obtained and these values were found to be in the order NaSPM > NiSPM > CuSPM > CuLPM and Cu-Y much greater than Ni-Y. The heats of reaction of NH3 on NaSPM were slightly lower than those on NiSPM, whereas those for Cu-Y were much higher than those for Ni-Y.