The Bureau of Mines developed a hydrometallurgical method for recovering mercury metal from mercury sulfide concentrates. Sulfide flotation concentrate from the McDermitt Mine was leached in a cupric chloride solution at 80 degrees c. The redox potential of the solution was maintained at 850 mv during leaching by chlorine sparging. Mercury extractions exceeded 99 pct in 3 h of leaching. After leaching, the ph of the solution was increased from 1 to 4.5 To precipitate copper as atacamite. The pregnant solution, typically containing 100 g/l hg, was sent to electrolysis to produce high-purity mercury metal and chlorine for recycle. In a 200-a electrolytic cell operated for 24 h, current efficiency was 99 pct, and the energy requirement was 0.9 Kw.H/lb of mercury produced. Mercury removal from the waste stream was also investigated. Iron or zinc cementation, sulfide precipitation with h2s, and activated carbon adsorption all decreased the mercury concentration from 10 g/l to 0.01 Mg/l, which is less than the Environmental Protection Agency limit on wastewater or 0.02 Mg/l.