Coal is still the major source of power for electrical generation worldwide and will continue to be in the foreseeable future. However, the inorganic elements in coal that qualify as hazardous emissions upon combustion of the coal become an increasingly important concern. Primary emphasis has been on postcombustion cleanup of these emissions, with no technology achieving overwhelming success. The precombustion technique reported here shows promise for removing trace elements as well as sulfur prior to burning the coal. This study shows that hydrothermal treatment need not be carried out at extreme conditions to effect such removal. The sulfur content and selected trace elements of some coals are reduced by 50% or more by water at conditions above the critical temperature but below the critical pressure. The study also shows that the technique was more effective on some coals than others. Results from a pilot-scale test are included in addition to bench-scale data.