Beypazari oil shale was subjected to conventional and free failing pyrolysis at different temperatures to investigate optimum liquefaction temperatures. The oils obtained were characterized by GC, (HNMR)-H-1, IR and size exclusion chromatography to follow the molecular changes induced by the pyrolysis. Free falling pyrolysis gave the maximum degree of conversion of 61.9% at 873 K, whereas conventional pyrolysis gave a degree of conversion of 50.5% at 773 K. Conventional pyrolysis gave less n-alkenes-1 than that obtained from free falling pyrolysis at similar temperature. Polymerization reactions are predominant during conventional pyrolysis due to the longer reaction time. In contrast to conventional pyrolysis, more cracking reactions occurred during the free falling pyrolysis. (C) 2002 Elsevier Science B.V. All rights reserved.