Deep vein thrombosis and the associated danger of pulmonary embolism are two manifestations of one disease. The frequency of deep vein thrombosis in operative medicine without medicinal prophylaxis varies between 14% and 32% and the resulting pulmonary embolism rate is approximately 0.8-6.2%. When deep vein thrombosis is suspected, a diagnostic clarification is carried out by determination of D-dimer levels, compression sonography of the veins and if necessary phlebography. When pulmonary embolism is suspected, the diagnostics are extended to computed tomography angiography (CTA) and if necessary echocardiography. If deep vein thrombosis and/or pulmonary embolism are present, therapy must be started immediately (full heparinization or systemic thrombolysis). The occurrence of deep vein thrombosis with subsequent pulmonary embolism can be reduced by consistent prophylaxis. The risk assessment incorporates exponential and dispositional risk factors. Prophylactic measures include early mobilization, compression stockings and in the highest risk group (radical prostatectomy and cystectomy) medicinal measures, as a rule low molecular weight heparins. Venous thromboembolism prophylaxis following such interventions should be continued postoperatively for 4-5 weeks.