Cutter roof failure, a ground control problem that frequently results in massive roof failure, is common in coal mines of the Northern Appalachian Coal Basin, causing delays in production and posing a safety hazard to mine personnel. The Bureau of Mines is conducting research on the causes of cutter roof failure to gain a basis from which to predict and prevent its occurrence, and to support such roof when failure occurs or is imminent. Research conducted at the Greenwich Collieries north and south mines in central Pennsylvania revealed a correlation between the presence of clastic dikes and formation of cutter roof failure. The research consisted of in-mine mapping of geologic and deformational features, rock pressure monitoring, core recovery and evaluation, and in situ stress measurement. It was found that roof failure increased in areas where the occurrence of clastic dikes was most frequent, especially where two or more clastic dikes intersect. Staggering of crosscuts prevented the extension of cutters and deterred the occurrence of large falls extending over several breakthroughs. In addition, trusses and cribbing were effective in stabilizing clastic dikes and inhibiting the development of cutter roof failure when employed immediately or shortly after mining.