The purpose of the study was to evaluate efficacy and safety of the new acute treatment of deep venous thrombosis by use of low-molecular-weight heparin compared with standard treatment using unfractionated heparin, especially concerning long-term morbidity.

Deep-venous thrombosis (DVT) remains a common clinical problem (annual incidence 0.10-0.16%) and long-term morbidity as chronic venous insufficience (CVI) in 10-30%.

As to recurrent DVT, initial treatment with Low-Molecular-Weight Heparin ( to-day's terminology Fractionated Heparin (FH)) and Unfractionated Heparin (UFH) has shown equal efficiency, whereas the efficacy concerning long-term morbidity has only more recently been published.

This study was initiated to compare the efficacy of UFH and FH concerning the incidence of CVI after symptomatic DVT at short-term and long-term follow-up.

Inclusion Criteria:

• First DVT with or without known risk factors except overt cancer
• Second DVT more than two years after the first if the patient was without clinical signs of CVI.

Exclusion Criteria:

• Contraindication to anticoagulation therapy
• Candidate to thrombectomy with arterious-venous fistula or thrombolytic therapy
• Known cancer at the time of the DVT diagnosis
• Patients unable to cooperate for anticoagulation therapy or manage the tests.