Aneurysmal bone cyst of the rib is a rare benign tumor which resembles the giant cell tumor or fibrous dysplasia of the bone. It rarely develops in the rib although it affects the metaphysis of the long bone and facial bone. We have treated a 14 year old male patient who had the aneurysmal bone cyst in the legt 4th. rib. Wide surgical resection of the affected rib was carried out with good clinical result. He is well 16 months after the resection.