Unfractionated heparin is effective in the treatment of deep venous thrombosis and pulmonary embolism but may lead to significant side-effects (bleeding complications and thrombocytopenia). Low molecular weight heparin fragments have been shown to be as effective as unfractionated heparins during prophylaxis with a once-daily injection regimen. The aim of this open study was to assess the tolerance and the efficacy of enoxaparin in established venous thromboembolism. The study included 36 consecutive patients (mean age 60 years) (range 13-87) with recent deep vein thrombosis (less than 5 days) documented by venography. All patients received enoxaparin twice daily at a fixed dosage of 2 mg/kg/day. The efficacy was assessed by the evolution of Arnesen venographic score. Seventeen patients showed a moderate improvement (less than 35%) and 17 patients had a marked improvement (over 35%). Two patients were not evaluated for efficacy because they displayed bleeding complications. No relationship was found between anti-Factor Xa level and regression of venographic score. In conclusion, subcutaneous administration of enoxaparin proved to be an effective antithrombotic therapy. A fixed dosage of 2 mg/kg/24 h should be the basis of the randomized controlled study ongoing at the present time.