Type III collagen is a fibrillar forming collagen comprising three α1(III) chains and is expressed in early embryos and throughout embryogenesis (PMID: 9050868). In the adult, type III collagen is a major component of the extracellular matrix in a variety of internal organs and skin. It occurs in most soft connective tissues along with type I collagen (PMID: 2445760). COL3A1 gene encodes type III procollagen. Mutations in this gene are associated with Ehlers-Danlos syndrome types IV, and with aortic and arterial aneurysms (PMID: 10706896; 2243125; 18389341). This antibody raised against 24-152 aa of prepro α1 (III) chain of human type III procollagen detects type III procollagen at 140-180 kDa and also in some lysates reveals a 70-kDa band which has been reported and may represent a cleaved form of type III procollagen.