Obstruction of the superior vena cava (SVC), a thin-walled vessel that carries blood at low pressure, may result from compression by tumor or intraluminal thrombus formation. The SVC syndrome that ensues may be the cause of significant morbidity. This article reviews the pathogenesis of SVC syndrome, appropriate radiologic imaging procedures, and the issue of obtaining a tissue diagnosis. The management of SVC syndrome with chemotherapy, radiotherapy, and surgery is also discussed.