Venous thromboembolism (VTE) is one of the most frequent multifactorial diseases. It manifests clinically by deep vein thrombosis (DVT) and pulmonary embolism (PE) leading to death in about 6%. It is important to emphasize, that 50% of the patients do not present any symptoms. The prevalence is influenced by age and ethnics. Both, hereditary (Factor V Leiden, G20210A prothrombin gene mutation, deficiencies of protein C, S or antithrombin) and acquired risk factors (estrogen replacement, cancer, cardiovascular disease, surgery, trauma, immobility, use of central venous catheters, autoimmune disease such as anti-phospholipid syndrome) contribute to VTE. The risk increases dramatically by the addition of hyperhomocysteinemia or the combination of several risk factors. Since VTE is a dynamic process able to manifest clinically or to resolve completely, the identification of persons at increased risk is mainly important for early diagnosis and treatment. The diagnostic strategy including clinical scores and laboratory tests (D-dimer measurement) as initial steps to confirm the suspicion of VTE may exclude patients who do not need further, sometimes invasive imaging tests (venography, compression ultrasonography combined or not combined with colour Doppler imaging, magnetic resonance imaging). Laboratory tests for suspected inherited thrombophilia should be performed six months after clinical presentation.