A randomized double-blind study comparing the efficacy and safety of two different dosage regimens of a low-MW heparin, Enoxaparin (Lovenox) 20 mg twice (group A) or 40 mg once (group B), was carried out in 103 elderly patients with a fracture of the neck of the femur. Distal and proximal thrombosis occurred in 18.3% of patients in group A and in 10.4% in group B. No major hemorrhagic complication was observed, except for two hematomas in each group. This trial suggests that a total daily dose of 40 mg of Enoxaparin can be effective in the prevention of deep vein thrombosis in elderly surgically treated patients and does not involve a major risk of bleeding.