Percolation leaching with a thiourea solution was investigated for processing a low-grade gold sulphide deposit (Bousquet V) belonging to the mining company Lac Minerals Ltd. Certain leaching parameters, such as percolation rate, thiourea concentration, oxidizing agent (H2O2, Fe3+) and granulometry were studied. To limit the phenomena of thiourea decomposition and to optimize gold extraction, it was necessary to maintain the leaching potential between 420 mV and 450 mV (S.H.E.). The maximum gold extraction in leaching the Bousquet V ore, after 75 days, varied between 76% (H2O2) and 83% (Fe3+), with thiourea consumption depended on the Tu/oxidizing agent concentration ratio and the nature of the oxidizing agent used. Acid consumption varied with ore granulometry (100 kg/t for -9.54 mm/ + 1.63 mm; 80 kg/t for - 19.04 mm/ + 1.63 mm).