Red degeneration of uterine leiomyoma (RDL) is hemorrhagic infarction caused by peripheral venous thrombosis. Peripheral high intensity rim on T1WI due to methemoglobin of blood products confined to thrombosed vessels is characteristic, however, it may not be observed at acute phase. We evaluated MR images including SWI of 17 RDL and 12 usual leiomyomas (UL). High intensity rim on T1WI, low intensity rim on T2WI and on SWI were observed in 47%, 47%, and 100% of RDL, whereas 0%, 8%, and 0% of UL, respectively. SWI may be helpful for the diagnosis of RDL in distinguishing from UL or sarcomas.