About 10% of all episodes of venous thrombosis are due to upper extremity deep vein thrombosis (UEDVT). Associated risk factors are indwelling central venous catheters, cancer, and coagulation defects; 20% of the episodes are unexplained. The onset of UEDVT is usually heralded by complaints such as arm swelling and pain, but may also be completely asymptomatic, especially in carriers of central venous lines. Objective confirmation is mandatory prior to instituting anticoagulation because the clinical diagnosis is unreliable; ultrasound-based methods represent the preferred diagnostic approach. Prophylaxis with low-dose heparin or low-dose warfarin may be used, especially in carriers of central venous catheters, although its efficacy is still uncertain. Unfractionated or low molecular weight heparins followed by oral anticoagulants should be regarded as the treatment of choice, whereas thrombolysis and surgery may be indicated in selected cases. Up to one third of the patients develop pulmonary embolism that may be fatal; postthrombotic syndrome and recurrent thromboembolism are also frequent complications. UEDVT should no longer be regarded as a rare and benign disease, as reported previously.