In the studies recently carried out on leather microbiology, a great deal of attention is paid to the fact that a considerable amount of fungi exist along with bacteria on the raw materials and in the pretanning processes and that they both have proteolytic and lypolytic activities. Because defects caused by fungi that mostly appear in tanning and post-tanning processes lead to drastic economical losses, it is important that fungi should be controlled from the initial steps of the manufacturing stages. To this end, bactericides with two different compositions (potassium dimethyl dithiocarbamate and quarternized compounds), and a fungicide (2-thiocyanomethylthio benzothiazole based) commonly used in Turkish leather industry were chosen. The bactericides were added into the main soaking float with and without different concentrations of fungicide. In each trial, liquor samples were taken at the end of the main soaking process and numbers of total aerobic mesophilic bacteria, the numbers of proteolytic and lypolytic bacteria, and numbers of total aerobic fungi, the numbers of proteolytic and lypolytic fungi were separately determined. When potassium dimethyl dithiocarbamate based bactericide at a ratio of 0.5% was used together with 2-(thiocyanomethylthio) benzothiazole based fungicide at a ratio of 0.5% in the main soaking process, it was found out that it was more effective against bacteria and fungi than when used alone. With the use of two antimicrobial agents in the aforesaid concentration, a synergistic effect appeared and whereas the number of fungi detected in the main soaking liquor decreased at a considerable level, all of the bacteria were controlled and so no bacterial growth occurred on the media.