Complex analytical methods have been developed for determining the chemical composition of fly ashes. Samples were collected at coal-fired power plants and municipal waste incinerators. Morphological investigations and single particle analysis were performed by SEM/EDAX method. A survey of mineralogical phases was made by X-ray powder diffraction and infrared spectrometry. Solvent-leaching experiments were carried out for the information on the mobility of metal pollutants under real environmental conditions. Copper, Ni, Co, Cr, Pb and Cd have been studied, and of the toxic metals, Cd has been found in exchangeable forms in a great amount. Mobile species of toxic metals may have an impact on the quality of receiving waters or on organisms in soils.