Due to the morbidity and mortality associated with either untreated disease or inappropriate anticoagulant therapy, accurate diagnosis of pulmonary embolism is essential. Pulmonary angiography, the current gold standard test for diagnosing pulmonary embolus, is both invasive and costly; therefore, noninvasive diagnostic strategies have been developed. Noninvasive tests often have to be combined to either raise the posttest probability of disease to a level justifying treatment or lower it to a level at which withholding treatment is warranted. Diagnostic algorithms involving clinical assessment; venous ultrasonography; D-dimer testing; ventilation-perfusion lung scanning; and, more recently, computed tomography have been validated in management trials of patients with a suspected pulmonary embolism. The optimal strategy at individual institutions is dependent on local availability, expertise, and cost. Magnetic resonance imaging and combined computed tomographic pulmonary angiography and venography possess the potential to be used as stand-alone tests for pulmonary embolism but require further evaluation.