Although cyanide is a widespread leaching reagent for the recovery of precious metals, there still are continuing investigations on alternative processes due to the related environmental problems concerned. Thiosulphate leaching of precious metals is one of the processes that were developed as an alternative and nontoxic technique to conventional cyanidation. The aim of this experimental study was to investigate the possibilities of leaching gold and silver in ammoniacal thiosulphate solutions on a laboratory scale. Samples used in the experiments were taken from Ovacik Gold Mine, located in the Bergama region of Turkey. The influence of temperature, copper sulphate concentration, ammonia concentration, thiosulphate concentration, sodium sulfite concentration, and solid-liquid ratio on gold and silver leaching recoveries was investigated and optimum leaching conditions were determined. At these conditions, 99.57% Au and 95.87% Ag leaching recoveries were achieved.