The Bureau of Mines conducted laboratory tests to determine the slurry transport and deposition properties of coal waste. A 188.5- Ft pipe test loop was constructed with instruments to measure density, flow, and power and discharge, suction, and differential pressures. A 20-ton sample of western coal waste was crushed and screened to 100 pct minus 1/2 in. Eight loop tests using this graded waste were run at slurry densities ranging from 1.15 (25 Wt- pct solids) to 1.46 (60 wt-pct solids). The resultant friction- pressure gradients ranged from 0.06 to 0.24 Ft of water per foot of 4-in standard steel pipe. Particle-size degradation was significant. In a typical loop test lasting 25 min, the minus 200- mesh fraction increased from 19 pct to 34 pct. Deposition tests showed that without the use of a flocculant, the slurries would not dewater when left to stand for 1 week. With flocculant, additional water was released; however, the settled slurries remained thixotropic. Further testing is necessary to determine their suitability for use as backfill material in active mines.