In the pregnant patient with suspected deep vein thrombosis (DVT) or pulmonary embolism (PE), accurate diagnosis is required to identify patients with DVT or PE who would benefit from appropriate anticoagulant therapy, and to exclude DVT and PE in the majority of patients so they are not exposed to the risks of anticoagulants. The diagnosis of DVT and PE during pregnancy is problematic. The use of invasive diagnostic tests, such as venography and pulmonary angiography, is limited because of the potential risks to the fetus of radiation exposure. Due to hemodynamic changes associated with pregnancy, noninvasive diagnostic tests such as impedance plethysmography and venous Doppler may be falsely abnormal. Diagnostic approaches for DVT and PE will be outlined that can accurately and safely confirm or exclude suspected DVT and PE during pregnancy.