Nowadays, technological development has ensured the welfare of human beings also, brought form hazardous problems to human health. One of these problems is pesticide residues that accumulate in the human bodies. Pesticides are used for plant protection and therefore are taken in through the contaminated food. This problem is not considered locally; because of the international commerce and transportation it has become a problem of the whole world. in this investigation, degradation of pesticides (Chlorpyrifos-metil, Chloridazon, Diazinon, Ethion, Methidation and Primicarb) by Saccharomyces cerevisiae WET 136 was studied. Degradation of pesticides by Saccharomyces cerevisiae WET 136 was studied in Yeast Ekstract Dextrose Broth (YEGB) incubated at 25 °C for 5 days. Uninoculated medium served as controls. At the different period of incubation (l, 2, 3, 4 and 5 days) pesticides were extracted with ethyl acetate (Merck) and analysed in a Packart gas chronıaîograph model 439 using a Nitrogen-Phosphorus specific detector. The pesticides used in this study Chlorpyrifos-methyl and Diazinon were degradated by Saccharomyces cerevisiae WET 136. The other pesticides were not degradated but Chloridazon, Chlorpyrifos methyl and Ethion were adsorbed on yeast.