Several methods have been developed to obtain oil from corn germ, oilseeds, and other oil-rich plant materials using aqueous enzymatic methods. Unlike traditional oil extraction methods, these new processes are performed without the use of presses and without organic solvents. Beginning with olives in ancient times, oil has been obtained from oil-rich plant materials. The large variations in cell wall ultrastructure and chemical composition (varying proportions of cellulose, hemicellulose and pectin) of oil-rich plant materials have created a challenge for the development of aqueous enzymatic oil extraction strategies. For most oil-rich plant materials, three types of enzymes (cellulases, proteases and pectinases) have proven to be most effective for the aqueous enzymatic oil extraction. Although the high cost of enzymes is a major hurdle to the commercialization of aqueous enzymatic oil extraction methods, recent advances in enzyme production technology are gradually reducing enzyme costs and bringing these technologies closer to becoming economically feasible.