The thermal behavior in argon of homogeneously synthesized cellulose p-toluenesulfonates (tosylates) with a degree of substitution (DS) ranging from 0.4 to 2.3 was studied by means of thermogravimetry and derivative thermogravimetry from ambient temperature up to 500 degrees C. For comparison, the thermal behavior of the starting celluloses used (pulps, linters, bacterial cellulose) was also examined. The thermal degradation of cellulose tosylates was initiated at lower temperature than cellulose itself and proceeds in two main stages. The temperature of the first one (169-196 degrees C) increases with increasing DS and is independent of the molecular weight. Activation energies calculated following the method of Broido, FTIR, and ultimate analysis as well as mass spectroscopy show that the first stage of degradation is closely associated not only with the scission of tosyl ester groups but also with a partially degradation of the polymer backbone. Further, the temperature-concentration diagram for the system cellulose tosylate 20/o-dichlorobenzene was studied by optical observations and calorimetric investigations. A liquid-liquid demixing interferes with the glass transition of the cellulose tosylate-solvent system. It results in the solidification of the solution.