Differential scanning calorimetry (DSC) was applied to determine the polymorphic conversion of famotidine in the compressed compactS after different compression treatments.Fourier transform infrared (FT-IR) microspectroscopy was also used to identify the polymorphic forms of famotidine.Two types of famotidine compacts were prepared by compressing a conical shape (compact Ⅰ) or a flat shape (compact Ⅱ) of famotidine form B powder bed.A drilled disc sample was prepared using a drill bit through the center of each famotidine compact, and determined by DSC analysis.The results clearly illustrate that all the compacts whether in the drilled disc Ⅰ or Ⅱ samples before DSC analysis were still consisted of the polymorphic form B of famotidine alone and was independent of compression applied,suggesting there was no polymorphic conversion of famotidine from form B to form A.Once the drilled disc sample was examined by DSC analysis, the drilled disc Ⅱ sample still remained the polymorphic form B of famotidine.However, the polymorphic conversion of famotidine in the transparent zone of compact Ⅰ under the heating process was occurred from form B to form A, suggesting the temperature accelerated the compression-induced polymorphic conversion of famotidine in the compact.