Massive ovarian edema (MOE) is a very rare disease characterized by a tumor-like enlargement of the ovary. The ultrasound findings have been reported as a solid tumor-like mass or as a solid mass containing a cystic component. Recent reports using magnetic resonance imaging of MOE have demonstrated that multiple ovarian follicles situated around the periphery of the cortex of the enlarged ovary is the most important diagnostic indicator of MOE. This finding was first demonstrated by ultrasound in the case we present here. Thus we suggest that the ultrasound detection of multiple peripheral ovarian follicles in a solid ovarian tumor-like mass may make the preoperative diagnosis of MOE possible by ultrasound alone.