Monitoring of pesticide residues in potato tubers and their prepared products (“pommes frites” and chips) was undertaken. Experiments were carried out to determine changes in concentration due to the washing, peeling and cooking process (blanching and frying) to assess the stability of pesticides in potatoes and their products. Pesticide residues were quantified by using gas chromatography. Results show that malathion, HCB, lindane and p,p-DDD were predominant in potatoes and their products. The highest mean was detected in potatoes, followed by pommes frites, while the lowest mean was recorded in chips. On the other hand, potato skin samples were found to contain the highest levels of DDT and its derivatives, lindane and HCB. Peeling was necessary to remove the greatest amount of pesticides in the skin. Washing with water and/or other solutions as well as the cooking process (blanching and frying) helped to eliminate most of the pesticide residues from the potato tubers.