Physicochemical properties of methyl p-hydroxybenzoate (MPHB) in a mixture with controlled-pore glass of 120 Angstrom (CPG120) were investigated by differential scanning calorimetry (DSC), powder X-ray diffraction measurement, and IR spectroscopy. In the DSC thermogram of a mixture of 40% MPHB and 60% CPG120, a broad endothermic peak(108-112 degrees C) and a sharp endothermic peak due to the fusion of MPHB were observed. In the following DSC run, the temperature of the endothermic peak (108-112 degrees C) was shifted to a lower temperature( 80-100 degrees C). The effects of grinding and atmospheric gas pressure on the DSC thermograms were also studied, Increase of the grinding time caused a decrease in the DSC peak area of fusion, and the adsorption of MPHB into the CPG pores was enhanced with grinding. The peak at 108-112 degrees C moved to higher temperatures in the condition of increased gas pressure. In the second DSC run, the temperature of the endothermic peak depended upon the pore size of the mixed CPG, These results indicated that MPHB in the mixture adsorbed into the pores of the CPG during the first DSC run and that the adsorbed and crystallized MPHB fused in the pores in the second run.