AbstractPolyclonal antibodies were raised in rabbits against a fusion peptide representing a portion of the amino‐terminal non‐triplehelical domain of mouse type XII collagen. The antibodies reacted with bands of 220 and 350 kDa on Western blots of mouse tissue extracts. Immunohistochemical analyses of mouse embryos demonstrated that type XII collagen is expressed mainly in dense connective tissues of tendons, ligaments, dermis, cornea, blood vessel walls, meninges, and developing membranous bones. Comparison of skin extracts and medium of cultured mouse skin fibroblasts by Western blotting showed that while tissues contain short 220 kDa type XII collagen polypeptides as well as the long form, cultured cells produce mainly the long form with 350 kDa polypeptides. © 1993 wiley‐Lis