In the Artvin-Kafkasor ore deposit gold and silver are the main precious metals and are associated with quartz and limonite. In the present investigation, a fungal culture isolated from a mine water was tested under laboratory conditions for its bioleaching potential for enhancing silver recovery prior to cyanidation. The silver recovery was expressed as both the silver dissolved after biotreatment and that recovered after cyanidation following biotreatment. Silver recovery increased as a function of fungal pretreatment time. After 40 days, silver recovery was about 83% (of which 15% was due to direct microbial action). The recovery by cyanidation alone, on the other hand (as observed with the uninoculated control), was 53%. These results suggest that the microbial action favours a more effective cyanidation by changing the physical properties of the ore.