Natural oils have a complex of oily substances extracted by various methods from plants, fruits or seeds without being mixed with products from chemical synthesis. The physicochemical properties of lipids, which have a special importance in food technology, are determined by their chemical composition and structure, which can be determined by establishing indices of normal chemical composition (iodine index, saponification index ) or freshness indicators (acidity index, peroxide index, p-anisidine index). In the paper are applied a series of chemical and physico-chemical methods for the analysis of commercially oils, with different origins and manufacturing methods. The analyzed oils were mixtures, derived from different oil plants: sunflower, grape seeds, olives, corn germ, pumpkin seeds, flax.