To elucidate whether or not a vitamin E-deficient diet affects the rat aorta extracellular matrix, we examined the alterations in glycosaminoglycans (GAGs), as one of the components of the extracellular matrix of the aorta. The total amount of uronic acid, as an index of GAG, decreased significantly in the aorta of vitamin E-deficient rats. The components of GAG were identified as hyaluronic acid (HA), heparan sulfate (HS), dermatan sulfate (DS) and chondroitin sulfate (CS) by electrophoresis together with enzymic digestion. The amount of sulfated GAGs, especially the amount of DS and CS, decreased in the aorta of vitamin E-deficient rats. The biosynthetic activity of GAG was determined by using [3H]glucosamine and [35S]sulfate. The total biosynthetic activity of GAG and the incorporation of [3H]glucosamine into HA, HS, DS and CS decreased markedly in the aorta of vitamin E-deficient rats. The decrease in the production of sulfated GAGs, especially DS, which is involved in the potent antithrombogenic activity, could be related to the lower anticoagulant activity in the aorta of vitamin E-deficient rats.