Limited literature and use history data have suggested that some high-chlorine Illinois coals do not cause boiler corrosion while extensive data developed by the British correlate corrosion with chlorine content and other parameters related to the coal and boiler. The differences in corrosivity in coals may be due to the coal properties, to blending of coals, or to the boiler parameters in which they were burned. The goals of this study focus on coal properties and are: (1) to characterize chlorine and other constituents in coals which have been reported to behave differently with respect to corrosion problems during combustion; (2) to determine the evolution profiles of chlorine-containing compounds in coals during pyrolysis and oxidation; and (3) to examine the behavior of Cl-, S-, N-, O-containing compounds in coal during pyrolysis. Proximate, ultimate, and ash composition analyses for all of the British and Illinois coal samples were completed in this quarter. Analysis of the acid-soluble sodium and potassium in coals is in progress. These data, along with ash composition data, will be used to assess a coal's relative corrosion potential. The HCl evolution profiles obtained from oxidation of the five Illinois coal samples were examined. The results indicate that temperatures of maximum HCl evolution range were 430°C to 450°C.