Calormetric measurements of the heat of adsorption of nonpolar molecules on VPI-5 were performed at 303 K and compared with the results of measurements of the same molecules on the silica faujasite (US-Ex). Both microporous adsorbents show similar adsorption behavior, which is due mainly to the fact that both solids are neutral and comparable in the diameter of the pores or cavities, respectively. The heat curves of ethane, n-butane, n-pentane, and n-hexane on VPI-5 are compared also with the corresponding curves on AIPO4-5 and AIPO4-11. From this comparison, it follows that the adsorption heat increases with increasing framework density (or decreasing pore diameter). With decreasing pore diameter, the entropy of the adsorbed molecules also decreases.