All major trials to-date provide strong evidence that, for the initial treatment of DVT, adjusted-dose LMWHs are at least as effective and safe as unfractionated heparin (UFH). When compared with UFH, LMWHs achieved better thrombus lysis and had less bleeding complications (21-91% risk reduction) and mortality (51% reduction). They also reduced the incidence of recurrent DVT and PE at 90 days follow-up while there was no need for monitoring. Despite these exciting findings however, long-term evaluation of mortality rate, recurrent venous thromboembolism, blood monitoring tests efficacy and thrombus propagation/reduction are open issues. Furthermore, venous haemodynamics have never been tested. There is an ongoing Canadian study today, aiming to determine LMWHs effectiveness in reducing death, recurrent venous thromboembolism and haemorrhagic complications; it is obvious however that further studies are needed. We must determine if a prolonged use of LMWHs (i.e. 90 days) is more effective in preventing the post-thrombotic sequelae, reducing also the incidence of haemorrhagic complications; we also need to know the nature of the haematological changes that develop and the relationship between these changes and the recurrence rate; and finally, we must identify effective blood tests to monitor this treatment.