Coal-fired power plants are a significant source of atmospheric mercury. In coal combustion flue gases, mercury can be adsorbed on fly ash, reducing the emission of mercury to the environment since fly ash is efficiently removed from the flue gas. The mechanism for adsorption on fly ash is not known. New analytical methods are being developed to identify the mercury species adsorbed on fly ash as well as on sorbent materials. In this paper, we present some results of X-Ray Absorption Fine Structure Spectroscopy (XAFS) measurements of unburned coal (char) exposed to mercury compounds in a simulated flue gas. When the gaseous mercury species was HgCl₂, the adsorbed form on char appeared to be a mercury-chlorine compound. When elemental mercury was the gaseous form, the form of mercury adsorbed on the char showed a dependence on the char composition. Preliminary analysis of the data indicates that chars exposed to elemental mercury may contain a mixture of elemental mercury and mercury chloride, depending on the amount of chlorine in the coal.