The U.S. Bureau of Mines conducted research to determine the relationship between current load and temperature rises in shielded and reeled coal mine trailing cables. Temperatures within and on the cables were measured with thermocouples, and the data were recorded over time by computer. Steady-state DC load tests with two type shd-gc cables revealed that only 3 to 7 pct more current, than Insulated Cable Engineers Association (ICEA) ratings for shielded cables, was required to reach rated insulation temperature. The ability of the metallic shielding to dissipate heat was reflected in longer thermal time constants than with unshielded designs. With a 25-pct duty cycle, nearly twice the continuous current was required to achieve an average insulation temperature of 90 deg c in a 20 deg c ambient. Steady-state temperature rises were then monitored in a two-conductor unshielded, flat cable wound on a shuttle car cable reel. Stabilized axial temperature profiles exhibited maxima midway between the reel flanges. Static derating factors, expressed as percentages of open-air ampacity, were considerably less than ICEA ratings for reeled cables. The findings support a tentative contention that deratings for trailing cables wound on reels should be based upon the specific cable configuration.