Susceptibility-weighted (SW) magnetic resonance (MR) sequences such as SWI (Susceptibility-Weighted Imaging) and SWAN (T2 Star-Weighted ANgiography) visualize the magnetic susceptibility effects generated by local inhomogeneity of the magnetic field as signal voids (1-4). SW sequences are more sensitive to the susceptibility difference between tissues than conventional T2*WI and have been used in imaging of central nervous system for evaluating the hemorrhage and small vessels (1-4). Recently clinical applications of SW sequences in body imaging were also reported (5-9). Fat-saturated T1WI is sensitive for subacute hemorrhage, however, it can only detect methemoglobin as high intensity due to paramagnetic effect. SW sequences have exquisite sensitivity to the blood products such as hemosiderin and deoxyhemoglobin, and may contribute to the diagnosis of various gynecologic pathologies with fresh, chronic or obsolete hemorrhage. The purpose of this exhibit is to demonstrate the role of SW sequences in diagnosing various pathologies in the female pelvis.Punctate or curved linear signal voids along the cyst wall on SW sequences due to hemosiderin deposition as a result of repeated hemorrhages are characteristic for ovarian endometrioma, and useful sign for differentiating from non-endometriotic hemorrhagic cyst (5) (Fig. 1). The presence of signal voids due to hemosiderin deposition in extra-ovarian endometriosis (i.e. urinary bladder, bowels, abdominal wall and peritoneal implants), and in adenomyosis is also diagnostic (6-8) (Fig. 2). SW sequences are sensitive to a small amount of hemorrhagic contents, and can differentiate mucinous cysts from hemorrhagic cysts both exhibiting high signal intensity on T1WI. SW sequences can also demonstrate fresh hemorrhage, and is helpful for detecting ectopic pregnancy with hemorrhage, and retained products of conception (RPOC) with hemorrhagic foci. Red degeneration of uterine leiomyoma is hemorrhagic infarction due to venous obstruction associated with pregnancy, and characteristic high intensity rim on T1WI corresponding to strongly paramagnetic methemoglobin within obstructed veins may appear at subacute phase of red degeneration. At acute phase high intensity rim on T1WI does not appear yet, however, low intensity rim on SW sequences corresponding to deoxyhemoglobin within obstructed veins may be helpful for the early diagnosis (Fig. 3). Hemorrhagic necrosis is often observed in high-grade malignancy with coagulative necrosis due to the breakdown of tumor vasculature, and demonstrating hemorrhagic necrosis within uterine myometrial mass on SW sequences may be suggestive for uterine sarcomas because intra-tumoral hemorrhage is rare in benign leiomyomas. However, both hemorrhage and calcification may appear as signal voids on SW sequences. Benign leiomyomas may often contain calcifications, which should be differentiated from intra-tumoral hemorrhage in sarcomas. Phase image of SW sequences can distinguish between paramagnetic iron in hemorrhage and diamagnetic calcium deposits in tissue (Fig. 4). Venous thrombus within the twisted vascular pedicle of ovarian torsion may appear as peripherally situated signal voids on SW sequences. This finding may be feasible for the diagnosis of ovarian torsion, particularly for the lesions with subacute or chronic course in which clinical diagnosis of torsion is difficult (9) (Fig. 5).SW sequences, which can be easily added to the routine MR examination protocol, are sensitive for the presence of hemorrhage within various gynecologic pathologies and may provide helpful information for the differential diagnosis.