The sulfur content of United States coal can be assessed using a variety of approaches. The sulfur content may be expressed in terms of total sulfur in the coal, pounds of sulfur per million Btu, or sulfur remaining after reduction by coal preparation. In addition, sulfur content may be applied to the demonstrated reserve base or to coal resource estimates. Unfortunately, current data bases do not allow for an integrated assessment at the national level. Although classification of coal resources and reserves according to sulfur content is arbitrary, preferential production of low-sulfur reserves will positively skew the total sulfur of the remaining coal resource.