Pelt obtained by deliming with peracetic acid can be chromed after additional treatment with sodium chloride or oxalic acid solution, or directly tanned using synthetic tannins. The results of differential scanning calorimetry and thermogravimetric analyses have suggested that any tanning increases thermal stability of leather collagen. The produced chrome-free leather, despite its high tensile strength, is not characterized by high shrinkage temperature what indicates insufficient thermal stability of such leather. This fact contradicts the results of differential scanning calorimetry and thermogravimetric analyses results which show the high thermal stability of the chrome-free leather. It has been concluded that scanning calorimetry and thermogravimetric analyses are not sufficient for the appropriate assessment of leather obtained by the methods of various tanning, and the conclusions about changes in leather structure and quality of leather can not be drawn only upon results of the mentioned analyses.