Thermal properties of 4,4'(2,2'-propylidene)-diphenol, referred to as bisphenol A, or BPA, are discussed. Parameters of thermal transitions were measured by DSC. The commercial product crystallizes in a-form crystals which melt at 157~ (onset) and 161~ (peak) with a heat of fusion 134.37 J g-l. Supercooled BPA shows a glass transition at about 40~ Almost identical results were obtained for samples recovered by different methods: flakes, pastilles and prills. Two new polymorphs, the 13 and 7-forms were identified. The [~-form melts at 131~ with a heat of fusion of 104.9 J g-l. The melting point of the ~-form was measured to be 138~ and its heat of fusion is 118.3 J g-I. Thermal conductivity of crystalline BPA was measured.