Active and residual subsidence over coal mines is an omnipresent threat to surface structures built before and/or after mining operations. The effect of subsidence can be mitigated by the placement of the correct fill during and/or after the mining operation. Fills, if properly selected and placed for the prevailing geologic and mining conditions, have the potential, during the mining operation, of functioning as an alternative ground control measure, increasing coal recovery, and enhancing ventilation control. During postabandonment, they serve the purpose of mitigating subsidence, preserving the hydrologic regime, minimizing underground mine fires, and enhancing postmining surface land use and value. Previous experiences with fills, both abroad and in the United States, are evaluated in terms of fill type, characteristics, mode of placement, problems, and effectiveness. The properties for fill materials desired in order to meet the design objectives are assessed. Fills commonly available at mine sites, and commercial admixtures that can enhance the characteristics of fill materials, are identified.