Castleman's disease is an uncommon disorder Occurring mostly in patients presenting with localized mediastinal lymphadenopathy. It is usually asymptornatic. With localized disease, Surgical excision is curative. Castleman's disease can very rarely present as superior vena cava syndrome. We describe a case of mediastinal Castleman's disease which presented as vena cava superior syndrome; it is the largest mediastinal mass from Castleman's disease reported in the literature.