Hemangiopericytoma in infants and children is usually benign. A case of recurrent hemangiopericytoma of the mediastinum in a 5-year-old boy is reported. The tumor recurred twice because of incomplete excision in the first instance. Immunohistochemistry of this enigmatic tumor is reviewed and ultrastructural features are described. The importance of total initial excision of the tumor and a prolonged follow-up is highlighted.