Pulmonary embolism and venous ischemia are acute complications of deep vein thrombosis (DVT) of the lower extremities. Delayed complications include a spectrum of debilitating symptoms referred to as postthrombotic syndrome (PST). Because the early symptoms and patient signs are nonspecific for DVT, careful history taking and radiological evaluation of the extent and migration of thrombus should be used to establish an objective diagnosis and the need for treatment. Anticoagulation therapy is recognized as the mainstay treatment in acute DVT. However, there are few data to suggest any major beneficial effect of the early clearing of massive DVT and PTS. Endovascular, catheter-directed, thrombolysis techniques, used alone or in combination with mechanical thrombectomy devices, have been proven to be highly effective in clearing acute DVT, which may allow the preservation of venous valve function and the prevention of subsequent venous occlusive disease. Definitive management of the underlying anatomic occlusive abnormalities should also be undertaken.