Due to the morbidity and mortality associated with either untreated disease or inappropriate anticoagulant therapy, accurate diagnosis of venous thromboembolism is essential. As venography, the current gold standard test for deep vein thrombosis (DVT), is both invasive and costly, noninvasive diagnostic strategies for diagnosing DVT have been developed. Noninvasive tests often have to be combined to either raise the post-test 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, and D-dimer testing have been validated in management trials of patients with DVT. The optimal strategy at individual institutions is dependent on local expertise and cost. Magnetic resonance venography has the potential to be used as a stand-alone test for DVT but requires further evaluation.