Mountaintop removal mining (MTRM) is a type of large-scale surface mining operation utilizing blasting and large earth-moving equipment to remove the rock layers and interbedded coal seams systematically downward from the tops of mountain ridges until levels are reached where it is no longer economically feasible to continue mining. During the mining operation the broken rock (mine waste) is placed in the steep heads of streams adjacent to the mountain ridges in disposal areas called "valley fills" (VF). A large region of steep terrain underlain by essentially horizontal, coal bearing rocks extending from eastern Kentucky northeastward through central southern West Virginia, is currently impacted by MTRM/VF. The environmental, economic, and societal impacts of MTRM/VF operations are currently the subject of intense public interest, controversy, litigation, legislative and regulatory consideration as well as ongoing scientific research. Past and current mining law and regulatory practice are generally site-specific and focus on individual permits rather than large-scale watershed and cumulative impacts of aggregated mining operations. New geologic, hydrologic and biologic research is now underway to address the larger-scale, cumulative impacts of MTRM/VF operations as well as site-specific issues of waste disposal, slope stability and reclamation. The results of those current investigations should provide a better basis for formulating public policy.