The diagnostic evaluation of the patient with suspected deep vein thrombosis (DVT) and pulmonary embolism (PE) is rapidly changing as the result of clinical studies that clarify the relationship between clinical features and the results of laboratory and imaging studies. The history and physical examination determine a clinical probability, which guides test selection and interpretation. Newly available diagnostic modalities allow greater diagnostic accuracy, lower cost, and greater convenience. New algorithms combine clinical features, the rapid ELISA (VIDAS) D-Dimer assay, compression ultrasonography, the ventilation/perfusion lung scan and spiral computed tomographic imaging.Morbidity and mortality studies indicate that 73% of PE diagnosed at autopsy were not detected clinically 1 and that PE has a mortality rate of 18% to 30% without treatment. 2 Over 90% of PE arise from DVT, and as many as 50% of patients with leg symptoms are proven to have a diagnosis other than DVT. 3-6 Classic symptoms for PE, such as pleuritic chest pain and hemoptysis, are not particularly useful in establishing the diagnosis of PE. 2 Clinical features alone are inadequate.Although often viewed as distinct clinical entities, DVT and PE represent manifestations of a continuum of disease. Over 50% of cases 7 of PE may not have recognized sources of DVT. Many patients with proximal DVT have clinically silent PE. Symptomatic thrombi are usually found in proximal veins 8,9 ; however, at least 50% of PE occurs in asymptomatic patients. 10 While the majority of DVT occurs in infrapopliteal veins, the primary source of PE is proximal DVT. 3,11-12 Calf DVT propagates proximally in about 20% to 30% of cases. 12 Predisposition to venous thromboembolic disease results from specific clinical conditions and hereditary and acquired blood defects. [13][14][15][16][17] High clinical probability occurs in malignancy, stasis, the postop-Traditional approaches to diagnosis of deep vein thrombosis and pulmonary embolism are primarily based on the results of compression ultrasonography and the ventilation/perfusion lung scan (V/Q). Spiral computed tomographic imaging may replace the V/Q scan, and the D-Dimer assay may guide evaluation.