Two oil shale samples from two different deposits in Jordan have been non-isothermally pyrolysed using a thermogravimetric analyser (TGA). The controlling parameters studied were the final pyrolysis temperature (up to 900 degrees C) and the influence of the heating rate (from 20 to 50 K min(-1)) as well as type of purge gas (N-2 or CO2) employed on the process of thermal degradation of the shale sample. The integral method was used in the analysis of TGA data in order to determine the pyrolysis kinetics. The main region of the sample＇s weight loss, arising from the conversion of organic matter to oil and gas, occurred within the temperature range 200 degrees C to 600 degrees C. The magnitude of the total weight loss was mainly dependent on the final temperature, as well as, to a lesser extent, on the heating rate employed. The rates of decomposition of the Ellujjun and Sultani oil shales changed significantly at a critical temperature of similar to 305 +/-15 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.