A study of the technical and economic feasibility of using a unique undercut and fill system developed by Bureau of Mines engineers to mine steeply pitching coal is discussed. The undercut and fill system combines hydraulic coal cutting with unassisted gravity fluming of the coal slurry. Mining occurs across strike and the extended entry is backfilled to provide uniform strata control and an impermeable water and air barrier. Subsequent mining occurs beneath the previously filled stope such that the roof consists of a solid, controlled back. In addition to providing positive roof and hanging wall support, the backfill system eliminates subsidence potential, postmining drainage, and the danger of spontaneous combustion from naturally drafting air currents. A throughflowing ventilation system permits passage of return air through the production face through ducting located at the backfill-coal junction thus providing a constant supply of fresh air at the face, eliminating the need for brattice cloths, and provides an additional excapeway for miners.