The effect of leaching temperature on metal release at wide range of pH for OS ash obtained at different ashing temperatures is shown in Figures 7-10. Generally, metal release is minor. More metal release is obtained at low pH. With increasing leaching temperatures, Oil Shale ashes show different patterns of metal release. At low pH, the leachability of the heavy metals analyzed is higher than those at higher pH. Analysis result on the effect of initial pH on final pH of the leachate (see Figure 11) suggests that irrespective of initial pH, except at initial pH < 1 (final pH = 2.4), the final pH is above 12. The acidic environment may be the reason for high metal release from the ash. Chro- mium and lead are the most released heavy metals with the exception at low pH,