LMWH preparations have been proven to be safe and effective in the out-patient management of acute DVT. Although LMWHs are more expensive than unfractionated heparin, the lack of need for laboratory monitoring of LMWHs and their potential for out-patient treatment more than offsets the drug related cost difference and results in a net cost savings in favour of LMWH. LMWHs have undergone limited investigation for the secondary prevention of venous thromboembolism after an initial in-patient course of unfractionated heparin. To data, LMWHs have been given in prophylactic doses in these trials. In this setting, the LMWHs are associated with a similar risk of bleeding as fixed, intermediate dose unfractionated heparin in patients with a high risk of bleeding. In patients with no increase in bleeding risk, fixed prophylactic dose LMWH appears to be associated with both a lower risk of bleeding than warfarin (target INR of 2.0 to 3.0) and an increased risk of recurrence, although these findings need to be confirmed in larger trials.