Subbituminous coals amount to over 25% of the National's coal reserves and are located in dry areas. Fluidized-bed combustion (FBC) offers a clean stack gas without additional water requirement. A western subituminous coal from the Rosebud mine in Montana was burned in the 18-inch diameter FBC unit at the Morgantown Energy Technology Center (METC) to investigate its potential as an FBC fuel. In this study, bed temperature ranged from about 1450 to 1670/sup 0/F and fluidizing air velocity ranged from 2.6 to 4 t per second. The investigation included operating characteristics, SO/sub 2/ emission with and without added limestone, distribution of solids and solid components throughout the system; other pertinent data are reported. Sulfur retention was greatest at lower bed temperatures (1450/sup 0/F). It was concluded that: sulfur dioxide emission can be kept below the EPA limit of 1.2 lb/10/sup 6/ Btu without any added sorbent for bed temperatures below 1500/sup 0/F; more stringent limits may require the addition of limestone. The NO/sub x/ emission limit of 0.6 lb NO/sub 2//10/sup 6/ Btu is met with excess air up to 25% and bed temperatures to 1670/sup 0/F. Alumina (Al/sub 2/O/sub 3/) builds up in the fluidized bed during operation increasing from about 18% in the coal ash to over 65% in the final bed of these runs. At bed temperatures over 1500/sup 0/F, some of the CaSO/sub 4/ particles formed are very fine and are rapidly carried out of the bed. Emissions from the 18-inch fluidized-bed combustor, including toxic trace elements and mutagenic activity, were comparable to or lower than those from conventional power plants.