A non-isothermal experimental study using thermogravimetric analysis (t.g.a.) was conducted to determine the overall kinetics of pyrolysis of three Turkish oil shales: Beypazan, Seyitomer and Himmetoglu. The integral method was used in the analysis of the t.g.a. data to determine first-order pyrolysis kinetics. Particle sizes of 0.7, 1.3 and 2.6 mm and final temperatures of 400, 550 and 700 degrees C were used. Himmetoglu oil shale was found to give better oil yields than the other two shales. The extent of pyrolysis was found to be practically independent of particle size for all the shales. The rates of decomposition of Seyitomer and Himmetoglu oil shales were found to change at critical temperatures of similar to 300 and similar to 350 degrees C respectively, Porosities and surface areas of raw and spent shales were also determined. Copyright (C) 1996 Elsevier Science Ltd.