Venous thromboembolism (VTE), thrombosis in the venous vasculature, causes considerable morbidity and mortality, and diagnosis and treatment are challenging. In this report we sought to summarize evidence on the following questions: 1) What are the efficacy and safety of low molecular weight heparin (LMWH) compared to unfractionated heparin (UFH) for treatment of deep venous thrombosis (DVT)? 2) What are the efficacy and safety of LMWH compared to UFH for treatment of pulmonary embolism (PE)? 3) What are the efficacy, safety, and cost-effectiveness of outpatient versus inpatient treatment of DVT with LMWH or UFH? 4) What is the optimal duration of treatment for DVT and PE? 5) How accurate are clinical prediction rules used for the diagnosis of DVT or PE? 6) What are the test characteristics of ultrasonography for diagnosis of DVT? 7) What are the test characteristics of helical computerized tomography (CT), magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA) for diagnosis of PE? 8) What are the test characteristics of D-dimer for diagnosis of VTE?