The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(e-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature ( T g ), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the T g of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymerpolymer interaction parameter, x 32 , was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of x 32 obtained for HSMS/ PCL blends has been compared with the value of x 32 for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends.