There is continuing interest in in situ production of oil from oil shale, particularly for deep deposits and for environmental reasons. Such production would involve long-time, low temperature pyrolysis. Accordingly, reactions of El-Lajjun oil shale have been carried out under N2 for 7, 14 and 28 days at temperatures in range 240–320 °C. The conversion plateaued at 300 °C and above at a value of about 80 wt% dmmf and was the same for 7 and 14 day pyrolysis. The total conversion decreased by 15% as the temperature decreased to 280 °C. The lower conversions at 240 and 260 °C were the same for 14 and 28 days but oil yield increased at the expense of asphaltene for the longer time. Sulfur content of the oil + asphaltene decreased with increasing reaction temperature (240–300 °C) and time (280–300 °C) from 13 wt% to a plateau of about 7 wt%. The characteristics of the oil and oil + asphaltene changed steadily with temperature up to 300 °C, but increasing the temperature further to 320