Oleic acid as its sodium salt is a major component of soap as an emulsifying agent. It is also used as emollient. Small amounts of oleic acid are used as an excipient in pharmaceuticals, oleic acid is used as an emulsifying or solubilizing agent in aerosol products. Small amounts of oleic acid are used as an excipient in pharmaceuticals. It is used as an emulsifying or solubilizing agent in aerosol products. Oleic acid have been shown to be important for the growth and productivity of Chinese Hamster cells. Functions of Oleic Acid in Cell Culture Systems: Long-term energy storage: energy derived from NADPH and ATP is stored in fatty acids. Fatty acids are esterified to a glycerol backbone to form a group of compounds known as mono-, di- and tri- glycerides (neutral fats). Energy is released when fatty acids are degraded. It is estimated that 40% of active substances are poorly soluble in water. The improvement of bio-availability of drugs with such properties presents one of the greatest challenges in drug formulations. This can be overcomed easily by using lipid based exciepients such as oleic acid to improve drug delivery system. Self emulsifying drug delivery system is one of the potential approaches for poorly soluble drugs which can be easily overcome by Oleic acid. Henceforth one can see a wide use of oleic acid as an excipient in drug delivery system.