Mercury in Indian coals belonging to different geological period and in some fly ash and bottom ash samples obtained from thermal power stations has been determined. A wide range of variations in mercury content from the value as low as 0.01 to as high as 1.5 ppm in coal samples have been observed. The fly ash and bottom ash samples mostly contain less than 0.005 ppm of mercury. The concentrations of mercury in different specific gravity fractions of four coal samples show that the metal is concentrated mostly in the fractions 1.6-1.7 and above 1.7 indicates its inorganic association in the fossil fuel.