Different genetic types of kaolinite were investigated from the point of view of crystallinity. The measurements were carried out by means of different methods of thermal analysis, infrared spectroscopy and X-ray diffraction. The different parameters of the degree of crystallinity based on a series of 85 nearly monomineralic samples were critically studied. The estimated parameters of the different methods show relatively bad correlation. The reason for the difference in the data come from the fact that the methods give information about different parts and/or features of the mineral structure. The results are better if several parameters are simultaneously used. In the present paper the results of thermal parameters are summarized.