We reviewed eleven cases with giant cell tumor of bone, which had been diagnosed since 1982. Of which, five cases had accompanying aneurysmal bone cysts. It has been known that some primary bone lesions could accompany aneurysmal bone cyst, and then recent informations about it tell that primary bone lesion may initiate, via its hemodynamic forces, the secondary reactive lesion of bone. Based on these findings, and confirming at least our three cases with aneurysmal bone cyst recurred, it seems to have certain correlationship between aggressiveness of giant cell tumor and aneurysmal bone cyst.