Many gold bearing ores throughout the western United States contain small quantities of mercury. The presence of mercury not only decreases the gold-loading capacity of the activated carbon, but complicates the fire refining of cathodes and creates a potential health hazard. The Bureau of Mines investigated methods to limit mercury extraction during gold ore leaching and to remove mercury from cyanide leach solutions. Mercury dissolution was reduced from 40 to 10 pct by decreasing nacn concentration from 20 lb to 0.34 Lb per ton of solution at a ph of <11. When 0.1 Lb cas per ton of ore was added to a leach slurry, mercury extraction was reduced from 27 to 0.4 pct. Less than 0.5 pct of the mercury was solubilized when <0.1 Lb cas per ton of ore, along with lime and nacn, was added to a simulated grinding circuit.