The sensitivity of FDG PET/CT will be established in patients with acute VTE. The accuracy with which sites of abnormal FDG uptake can be related, spatially, to vascular structures will be critical to the success of this study. There is little doubt that this can better be accomplished with PET/CT than with PET alone. PET/CT will be used for all of these studies. Patients with documented acute VTE, will be enrolled. To determine the utility of FDG PET/CT in distinguishing acute from subacute or chronic clot, and to establish the extent of acute clot, the initial whole body PET/CT scan must be performed within 2 weeks of onset of symptoms of DVT, and subsequent limited region PET/CT scans will be performed at 2-3 weeks and at 6 weeks following the initial PET/CT scan. Whenever possible, subjects will be recruited who have unprovoked VTE because the potential benefit to the patient for participating in this study will be greatest for these patients are at a higher risk for harboring an underlying occult malignancy. However, patients with both provoked and unprovoked VTE will be eligible for enrollment under this specific aim.