Low-molecular-weight heparins (LMWH) have different properties than non-fractionated heparins. Bioavailability is better after subcutaneous administration and a longer halflife allows a single daily injection. Efficacy is equivalent for postoperative thromboembolism prophylaxis for all types of surgery. In most reports, low-molecular-weight heparins are more effective than non fractionated heparin and lead to fewer episodes of hemorrhage and thrombocytopenia. For treatment of deep vein thrombosis, low-molecular-weight heparins are as effective as non-fractionated heparins after two, or even one, daily injection without hemostasis tests. Other on-going studies are evaluating LMWH indications in pulmonary embolism, artery disease, pregnancy or other medical conditions.