With current high-resolution equipment and proper case selection, intravenous digital subtraction angiography (IVDSA) can consistently demonstrate pulmonary emboli greater than 2.0 mm in size. IVDSA is less traumatic than conventional pulmonary angiography and is preferable for high-risk cases such as patients with pulmonary arterial hypertension. For successful IVDSA studies patients should be able to hold their breath for 10 to 20 seconds. IVDSA should not be used in patients who are extremely dyspneic, who cannot suppress a cough, or who have a low cardiac output. In these instances selective intraarterial DSA is preferable.