Recently, leaching of gold with cyanide has come under scrutiny for its possible detrimental effects to the environment. Also, in some gold bearing ores and concentrates, conventional cyanide leaching is not the best method for gold extraction. This is due to gold particle encapsulation, cyanicides or pregrobbing carbon such as found in refractory ores and concentrates. Hence, there is much interest in developing an alternative way to extract gold from ore. Possible benefits of leaching gold with something other than cyanide include easier processing of refractory ore bodies including: carbonaceous, cyanicides, and sulfides, cheaper reagent and operating costs and opening of mine properties in places where cyanide use has been limited by the law. Hence, this paper details the fundamentals and development of the Alkaline Sulfide Gold Leaching system. (C) 2016 Elsevier Ltd. All rights reserved.