Elastin is a polymeric protein found in connective tissue which imparts the property of elasticity to vertebrate elastic tissue. It is synthesized and secreted as a soluble, single-chain protein (tropoelastin) which undergoes a number of post-ribosomal modifications prior to its organization into an elastic fiber in the extracellular space. Once secreted, tropoelastin molecules are joined covalently via chemical modification and cross-linking of specific lysyl residues to form the mature insoluble elastin. Ultrastructurally, it is predominantly an amorphous material which may change its morphology with ageing and different disease states. The abnormal accumulation of elastic tissue in blood vessels is found in atherosclerosis and hypertension. Genetic defects in the elastin molecule are reported to lead to inherited diseases such as Marfan's syndrome, pseudoxanthoma elasticum and the Bushke-Ollendorf syndrome.