Heparins, dermatan sulfate (DS), and Orgaran are the only glycosaminoglycans that have been used as antithrombotic agents in man. The largest experience concerns unfractionated heparin (UH) and its low-molecular-weight derivatives (LMWHs). It is firmly established that UH is efficient and safe in the prevention and treatment of deep vein thrombosis (DVT). Unfractionated heparin is also used as adjunctive therapy in the treatment of arterial thrombosis. Meta-analyses have shown that LMWHs are slightly more efficient than UH. Because they are more convenient for the nurses and the patient, and because they probably induce less bleeding and less immunogallergic thrombocytopenia, they will progressively replace UH in these indications. Clinical experience with DS is still scarce. Unfractionated DS has a low bioavailability after s.c. or i.m. administration; thus, LMW-DS are presently developed. These compounds have a low prohemorrhagic potential, and it has been proven that they are efficient in the prevention of postoperative DVT. Orgaran is a complex mixture of several glycosaminoglycans, excluding heparin. This compound has been found efficient in the prevention and treatment of DVT. Interestingly, in patients presenting heparin-induced thrombocytopenia, Orgaran may be an alternative treatment because a cross-reactivity with heparin is observed in less than 10% of the subjects.