Gold can be effectively extracted from various sources such as refractory ores and jewelry scrap by dissolution in ammoniacal solutions with the aid of appropriate oxidants. Electrochemical and kinetic aspects of the dissolution of gold from the elemental state and various ores in ammoniacal solutions are presented and discussed in this paper. The role of a number of oxidants including oxygen, cupric ammine, cobaltic ammine, and iodine has been examined and discussed. Also included in the discussion is the effect of concentration of free ammonia, ammonium ion and other salts on the overall rate of dissolution of gold. Excellent dissolution yielding better than 95% gold and silver recovery from sulfidic and carbonaceous refractory ores after I to 2 h of leaching at about 160 degrees C to 190 degrees C is possible in a single stage operation, Gold dissolution is affected greatly by reaction temperature and concentration of ammonia and oxidants. (C) 2000 Elsevier Science B.V. All rights reserved.