LMWH has been compared with unfractionated heparin in the treatment of venous thrombosis. The results of a pooled analysis studies of hospitalized patients showed a significant reduction of thrombus size, p < 0.001 and in the incidence of recurrent venous thromboembolism, p < 0.001 and of major bleeding p < 0.005 in patients treated with LMWH. The pooled mortality rate at long term follow-up was also found to be lower in LMWH group. Two large randomized trials have been completed in which LMWH was administered subcutaneously on an outpatient basis and compared with the standard approach of unfractionated heparin administered by continuous intravenous infusion in hospital. In both studies the efficacy, safety and mortality in the LMWH and heparin groups were similar.