Castleman's disease, giant lymph node hyperplasia, is a rare benign tumor which was originally reported by Castleman in 1956. It has two types of pathological characteristics of hyaline-vascular and plasma cell. Surgery is usually perferred because of the giant mass shadow on the chest roentgenogram rather than symptomes it causes. It is cured completely by resection without recurrence. We have experienced a case of Castleman's disease in the right anterosuperior mediastinum in a 36-year-old female. She was treated by surgical resection with good result She is well one year after surgeny.