Adult and foetal bovine vitreous were analyzed for the presence of unprocessed and partially processed forms of type II procollagen. Type II procollagen can exist in two alternatively spliced forms: a short form which lacks a large part of the N-propeptide due to the splicing out of exon 2 and a long form in which exon 2 is expressed and which has a full-sized N-propeptide. Both splice variants were demonstrated and analyses of type II pN-collagen demonstrated that the long form predominated, the ratio of the long form to the short form being 5:1 in foetal vitreous and 1.5:1 in adult vitreous. In foetal vitreous 35% of the type II collagen extracted was in the pN form, but there was very little unprocessed type II procollagen or type II pC-collagen. In contrast, adult vitreous extracts contained relatively less type II pN-collagen, but contained larger amounts of type II pC-collagen and unprocessed type II procollagen.