An optimum thermal decomposition (retorting) of the Jordanian Lajjun oil shale was examined using a laboratory-scale batch-loaded fluidized-bed reactor. The effects of the retorting temperature (450-600 degrees C), shale hold time (5-40 min) and size of shale particle (0.6-4.5 mm) on oil yield were investigated. Findings showed that for maximum oil yield achievement, a shale particle size close to 1.4 mm was optimal. For this, two optimum retorting zones were proposed; in the first zone, retorting should be performed at higher temperatures (540-600 degrees C) and short shale hold times (5-20 min) and in the second zone, at lower temperatures (450-510 degrees C) and long hold times (> 20-40 min).