This chapter considers storage proteins for which storage is the main, and in most cases only, function. It defines storage proteins as those that are present in insoluble deposits, which exhibit tissue specificity and whose synthesis is regulated by availability of mineral nutrients, although the latter character has not been studied for all components. Prolamins are the major storage proteins in all cereals except oats and rice and have consequently been the most widely studied. They are most conveniently considered in four groups: the Triticeae, oats, rice, and the Panicoideae. Because of their unusual amino acid compositions and solubility properties the prolamins were long considered to be a unique group that had evolved within the Gramineae. A major stimulus to research on cereal seed proteins is, of course, their economic importance in determining the nutritional and technological quality of the grain. The total amount of storage protein is, of course, determined to a large extent by genetic factors.