Conversion of used sunflower oil was carried out thermal and in the presence of different catalysts (Na-2 CO3, silica- alumina, and HZSM- 5) in a reactor ( #316 SS tubing, 210 mm long, 45mm i.d.) equipped with thermocouples, inert gas connection and packed fractionating column (#316 SS tubing, 540mm, 45mm i.d., packed with ceramic rings having 7mm i.d.). The products consisted of gaseous and liquid hydrocarbons, carboxylic acids, CO, CO2, H-2, water, coke, and residual oil. Highest conversion of oil ( 73.2%) and the maximum amount of the liquid hydrocarbon product ( 32.8%) were obtained at 420 degrees C with Na-2 CO3 as catalyst. The liquid hydrocarbon products consisted mainly of hydrocarbons in the gasoline boiling range. (C) 1998 Elsevier Science Ltd. All rights reserved.