Objectives: Non-alcoholic fatty liver disease (NAFLD) is characterized by increased fatty acid levels in serum and liver. The mechanism of NAFLD is unclear. The role of endoplasmic reticulum (ER) stress attracts attention. First aim of this study was to design an in vitro NAFLD model. The effects of palmitic acid (PA) alone or combination with oleic acid (OA) on intracellular reactive oxygen species (ROS) production and ER stress in liver cells were investigated as a second aim.