Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment and one of the commonest autosomal dominant connective tissue dysplasias. There is clinical and locus heterogeneity with about two thirds of families linked to the gene encoding type II procollagen (COL2A1). Families with Sticklers syndrome type 1 have a characteristic congenital vitreous anomaly and are linked without recombination to markers at the COL2A1 locus. In contrast families with the type 2 variety have a different vitreo-retinal phenotype and are not linked to the COL2A1 gene. Type XI collagen is a quantitatively minor fibrillar collagen related to type V collagen and associated with the more abundant type II collagen fibrils. A mutation in COL11A2, the gene for alpha 2 (XI) procollagen, has recently been found in a family described as having Stickler syndrome, although there was no ocular involvement. Here we show for the first time that a family with the full Type 2 Stickler syndrome including vitreous and retinal abnormalities is linked to the COL11A1 gene and characterise the mutation as a Glycine to Valine substitution at position 97 of the triple helical domain caused by a single base G-->T mutation. These results are the first to provide confirmation that type XI collagen is an important structural component of human vitreous. They also support previous work suggesting that mutations in the genes encoding collagen XI can give rise to some manifestations of Stickler syndrome, but of these, only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features.