Tests and analyses were conducted to characterize the physical, chemical, exothermic, and leaching properties of solid residues from bubbling bed atmospheric fluidized bed combustion units. The residues were produced during the combustion of eastern Canadian high-sulphur bituminous coals (4–8% sulphur) in a bed of eastern Canadian limestone. The residues were highly buffered and composed primarily of calcium and sulphur salts. They were exothermic and swelled considerably when contacted with water. Leachates generated during 20-cycle serial batch leaching tests were highly alkaline with high total dissolved solids concentrations, primarily calcium and sulphate ions. Column leaching test results and field observations suggest reactions may continue to occur over several months until the residues eventually solidify. The residues have properties that are unique, in comparison with conventional pulverized coal combustion wastes.Key words: fluidized bed combustion, ash, leaching.