Here represents a case of aneurysmal bone cyst which is very rare non neoplastic bone tumor especially in rib. The aneurysmal bone cyst usually arises from long bones of the upper and lower extemities and tt-e spine, which together account for 60 to 70 per cent of cases. In this case the tumor is found in right ninth rib on routine chest X-ray. It is resected successfully and the result is excellent.[KTCS 1977;2:226-229]