Warfarin remains the standard drug for secondary prophylaxis following venous thromboembolism, however this treatment is not ideal. In patients for whom monitoring is problematic or who have a high risk of bleeding complications, other possible solutions have been explored. Unfractionated heparin has been used to a limited extent in these situations and requires dose adjustment in order to achieve an acceptable efficacy. Low-molecular-weight heparin (LMWH) is a valuable alternative to warfarin for these patients and for thromboprophylaxis during pregnancy. In several subgroups of patients with venous thromboembolism the use of a LMWH instead of warfarin could offer specific advantages. The combination of warfarin and LMWH is warranted in patients for whom it is predicted that warfarin treatment alone may fail. The optimal dose of LMWH in long-term prophylaxis has not been evaluated in a properly designed study and the optimal duration of prophylaxis with LMWH is thought to be similar to that for warfarin.