Azlactones may be considered the anhydrides of alpha-acylamino acids. It is convenient to classify them into two groups, saturated and unsaturated, since the two types show characteristic differences in properties, Azlactones have been of interest mainly as intermediates in the synthesis of other compounds. Saturated azlactones are obtained most often from the corresponding amino acids used in preparing derivatives of those amino acids. Unsaturated azlactones, on the other hand, usually are prepared by condensing an aldehyde with an acylglycine and are used in the synthesis of the corresponding amino and keto acids. Four methods by which azlactones are prepared are discussed in this chapter.