It is known that the concentration of elements of fly ash varies due to the used-coal and the used-lime qualities varying in different periods. In the Can Thermal Power Plant (CTPP) located at northwestern Turkey, Can (Canakkale) basin coals, which are classified as lignite to sub-bituminous C coal with high total sulphur (0.4-12.22%) and a broad range of ash contents (3.2-44.6%) are mainly used. Performed studies reveal that some toxic elements exit in the coal, including As, U and V. Also, while the As, Cu, Co and Hg contents in coal increases, the sulphur contents in coal also increase. Additionally, trace elements that have inorganic compounds in coal are mobilized into air during the combustion process. This poses a big risk for human health and keeping the environment when Can Basins low quality lignite is burned, it's the fly ash that contains several toxic elements which can leach out and contaminate the water resources. In this study, toxicity tests were conducted on the fly ash samples that were obtained from the fluidized bed combustion of Can Thermal Power Plant. The results showed that water temperature, pH and the quality of the limestone used were the most important factors affecting the leaching properties. Concentration of some toxic elements found in the fly ash, such as; As, Cd, Cr, Pb, Se and Zn were analyzed. Concentration richness of some heavy metals were attributed to the increase of water temperature, especially when pH is lower than 5. At pH = 5 value, there is no clear explanation of each heavy metal presence in the fly ash from fluidized bed combustion thermal power plant. (C) 2010 Elsevier B.V. All rights reserved.