Cyanide has long been looked upon as the classical poison and has been listed by EPA as a priority pollutant. The mineral dressing industry has long used cyanide in its concentration and extractive metallurgy operations. Cyanide plays a role of varying importance in the metallurgy of gold, silver, copper, nickel, cobalt, lead, zinc, molybdenum, and cadmium. In the copper, lead, and zinc industries the primary uses for cyanides are as depressants for the flotation of iron and zinc minerals and for the reactivation of copper minerals in the flotation of molybdenite. This study was made to determine the technical, and if possible, the economic feasibility of substituting alternative reagents for cyanides as depressants for iron in the flotation of copper, lead, and zinc ores. The study was carried out in two phases. The first consisted of a literature search, an evaluation of the data obtained in the search, and finally a suite of laboratory-scale flotation experiments to test the three selected reagents. These experiments were made on copper ores, copper-lead-zinc ores, and zinc ores supplied by industry. The three reagents selected and tested were sodium sulfite, sodium sulfide, and sodium thiosulfate. Phase II consisted of interviewing company officials and operators in the copper-lead-zinc industry. Visits were made to 11 companies operating 17 mills in these fields.