The Bureau of Mines conducted laboratory tests to devise a procedure for extracting copper from low-grade discarded mill tailings. A solid extractant consisting of an organic solvent extraction reagent adsorbed on granular activated carbon was investigated and proved to be satisfactory for extracting copper directly from leach pulps. When this material was used in a cyclic leaching, stripping, and electrowinning process, 95 pct of the acid-soluble copper was recovered from oxidized mill tailings. The weathered tailings contained 0.24 pct cu (total) and 0.20 pct acid-soluble cu. The copper was recovered as cathodes containing, in parts per millon, 1.6 PB, 3.6 Fe, 0.5 Sb, 1.5 Al, 1.9 Mn, and <1 mg.