PURPOSE: The purpose of this study is to determine whether MRI is helpful for differentiating torsion of ovarian tumor, with or without necrosis MATERIALS AND METHODS: We retrospectively evaluated the MRI findings of nine patients with surgically confirmed torsion of the ovarian tumor, comparing them with the surgical and pathologic findings. The MRI findings were analyzed for contrast enhancement of twisted tumor, and the presence, signal intensity and contrast enhancement of twisted vascular pedicle. RESULTS: In all nine patients, MRI revealed a twisted vascular pedicle. Six patients with necrotic ovaries showed either no enhancement (n=4) or linear peripheral enhancement of twisted tumors (n=2), and lack of enhancement (n=5) or peripheral enhancement(n=1) of twisted vascular pedicles. In four of six patients with necrosis, T1-weighted MR images demonstrated a hyperintense pedicle; in three without necrosis, postcon-trast T1-weighted MR images revealed well-enhanced twisted tumors (n=2) and twisted vascular pedicles (n=3). CONCLUSION: By depicting a lack of contrast enhancement and high signal intensity within a twisted vascular pedicle, MRI can help differentiate torsion of ovarian tumor with or without necrosis.