The review of recent literature relating to the use of thiourea as a lixiviant for gold and silver indicates only a modest level of activity and interest. Alkali cyanide leaching system remains the popular choice for treating gold and silver ores. There is some interest in using thiourea as an alternative to cyanide in the processing of high grade concentrates. Thiourea does have potential for extracting gold and silver from refractory ores and concentrates that have sufficient value to justify the use of thiourea as a reagent. As illustrated by the leaching results for the bulk concentrate reported in this article, thiourea yields substantially higher levels of gold and silver extraction than does cyanide. Dissolution is generally much faster in thiourea than in cyanide solution.