Samples of Ellajjun oil shale were pyrolysed under nitrogen environment to the final pyrolysis temperature of 550 °C. The particle size of the samples under study was varied from 10 to 40 mm. The effect of particle size on weight loss and oil yield was investigated at a constant heating rate of 2-3 °C/min. Increasing particle size from 10 to 40 mm decreased the total sample weight loss from 27 to 21% at the same final pyrolysis temperature. At the same time, gas weight loss decreased from 10 to 6%. Oil yield was found to decrease with increasing particle size in the studied range from 92 to 70%.The shale oil produced was distilled in a simple atmospheric distillation unit to give naphtha, gasoline, diesel and residue. The naphtha fraction was found to decrease with increasing particle size. The diesel fraction decreased by 8%, i.e. from 50 to 42%, when particle size was increased from 10 to 40 mm. The kerosine percentage decreased from 35 to 22% with increasing particle size.