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 α-form crystals which melt at 157°C (onset) and 161°C (peak) with a heat of fusion 134.37 J g−1. Supercooled BPA shows a glass transition at about 40°C. Almost identical results were obtained for samples recovered by different methods: flakes, pastilles and prills. Two new polymorphs, the β and γ-forms were identified. The β-form melts at 131°C with a heat of fusion of 104.9 J g−1. The melting point of the γ-form was measured to be 138°C and its heat of fusion is 118.3 J g−1. Thermal conductivity of crystalline BPA was measured.