Although ultrasound has not been used to clarify bone lesions because of their high acoustic impendence and attenuation coefficient, aneurysmal bone cyst of the pelvis was imaged with ultrasound. Dual fluid levels and multiple loculations were discovered by ultrasound imaging through thin cortical bone. Ultrasonography is a simple, non-invasive method which can be utilized to detect bony lesions of an expansile nature and reveal characteric findings in an aneurysmal bone cyst.