We provide the first biochemical characterisation of intact type IX collagen extracted from bovine vitreous. It possesses a shortened α1(IX) chain (Mr 64K) compared to its cartilage counterpart (Mr 84K). All the vitreous type IX collagen is in a proteoglycan form, its glycosaminoglycan constituent being a chondroitin/dermatan sulphate component of Mr 15-60K attached to the α2(IX) chain. This contrasts with previous findings in chick vitreous where a very long glycosaminoglycan chain of Mr ∼350K was demonstrated. © 1992 Academic Press, Inc.