We report a rare case of expansile leiomyoma arising from the ilium of a 12-year-old girl. A plain radiographand CT both showed a lesion consisting of a well-defined area of expansile soft tissue mass with a thin scleroticrim and septae, surrounded by thin overlying cortex. MRI revealed a well-defined area of inhomogeneously higher signal intensity than that of surrounding muscle but of similar signal intensity than that of the red marrow of the opposite ilium on proton and T2W1. Inhomogeneous but intense enhancement was noted on Gd-enhanced T1W1. Angiography revealed hypervascularity and tumor staining. Microscopic examination on immunochemical staining with actin revealed a spindle cell tumor supporting the smooth muscle cell origin of the mass.