A deep-cutting continuous miner was tested under production-mining conditions at the Joanne Mine, Rachel, West Virginia, for about 1- 1/2 years (226 production days). The miner was run in a low-head revolution per minute, deep-cutting mode and a high revolution per minute, shallow-cutting mode. The tests confirmed that deep cutting and slow cutter speed reduce respirable dust significantly under production-mining conditions. Quantitative reductions in dust, in deep versus shallow cutting, were 73 percent in return air and 63 percent at the operator's location. Production rate (tons per shift) and bit consumption rate did not show any relationship to deep or shallow cutting. Reliability and maintainability of the miner were worse in deep-cutting mode because of cutter drive shaft failures; the cutter shaft problem was solved through improved material and design. Except for cutter shaft repairs, maintainability was similar for deep and shallow cutting.