The antithrombotic activity of dermatan sulfate from avian crown with the mean molecular weight of 38000 was compared to those from bovine intestine with the mean molecular weight of 16000 in vivo and in vitro. In an in vitro test. bovine intestine dermatan sulfate exhibited stronger effects on stimulation of heparin cofactor II and activation of Glu-plasminogen by tissue plasminogen activator. In vivo, avian crown dermatan sulfate more effectively prevented the development of thrombus in a rat deep vein thrombosis model, The measurement of plasma levels of these two kinds of dermatan sulfate revealed that avian crown dermatan sulfate circulated in higher concentration and longer duration than bovine intestine dermatan sulfate after intravenous administration to rats. (C) 1999 Elsevier Science Ltd. All rights reserved.