Underground coal mining (down to (approx.)0.75 km depth) in the contiguous Wasatch Plateau (WP) and Book Cliffs (BC) mining districts of east-central Utah induces abundant seismicity that is monitored by the University of Utah regional seismic network. This report presents the results of a systematic characterization of mining seismicity (magnitude 4.2) in the WP-BC region from January 1978 to June 2000--together with an evaluation of three seismic events (magnitude 4.3) associated with underground trona mining in southwestern Wyoming during January-August 2000. (Unless specified otherwise, magnitude implies Richter local magnitude, M(sub L).) The University of Utah Seismograph Stations (UUSS) undertook this cooperative project to assist the University of California Lawrence Livermore National Laboratory (LLNL) in research and development relating to monitoring the Comprehensive Test Ban Treaty (CTBT).