Abstract: Efficiency of natural oil i.e. red pepper oil against auto and photo-oxidative deterioration of sunflower and soybean oil was studied. The results showed a marked increase in peroxide value and free fatty acids during storage under fluorescent light, ambient and dark conditions. Applications of synthetic antioxidants i.e. butilated hydroxy toluene (BHT) and a natural antioxidant of red pepper oil have markedly reduced the rate of peroxidation in oils during exposure to light for five weeks storage. However, the BHT proved better antioxidation influence than red pepper oil. However, the effect of red pepper oil was also found acceptable in retarding rancidity occurred by per oxide value, free fatty acids and color value.