interventions have shown that even at a relatively low anticoagulant level the LMWHs are as effective as unfractionated heparin at the recommended dosages which produce a relatively higher level of anticoagulation (ACT /200 secs.). Thus, these agents are currently being developed for several intervenous/ hematologic indications such as bone marrow transplantation and blood cancers. It should be emphasized that different LMWHs produce different degrees of anticoagulation and should therefore be individually optimized for a specific hematologic indication. At a relatively high dosage the levels of LMWHs can be measured by using the ACT and APTT. LMWHs will find expanded indications in both the medical and surgical management of patients with hematologic and oncologic disorders. The LMWHs are also useful in the management of cancer patients. Recent trials have clearly shown that these drugs reduce the mortality outcome in cancer patients. The only approved anti-Xa drug is represented by a synthetic heparinomimetic, namely, fondaparinux † . This drug is given for the prophylaxis of post orthopedic indications. This agent is undergoing additional clinical trials in the management of several other indications. Because of the dependence on antithrombin (AT) and the sole anti-Xa effects, it has a narrow therapeutic index and its efficacy in this indication may be limited. Additional clinical trials are needed at this time to validate the clinical potential of this drug. The long lasting methylated pentasaccharide derivative, namely idraparinux, is also being optimally developed; however, there is no antidote for this agent. The antithrombin agents (hirudin, hirulog and argatroban) were initially developed for arterial indications. However, these agents are approved as a substitute anticoagulant in patients with heparin induced thrombocytopenia (HIT) and PCI. Different antithrombin agents produce their therapeutic effects by distinct mechanisms and should be considered equivalent on the basis of their antic