PURPOSE: To describe the features of twisted ovarian tumors on com- puted tomographic (CT) scans and magnetic resonance (MR) images. MATERIALS AND METHODS: The CT scans, MR images, clinical records, and histopathologic findings in 10 patients urlth surgical proof of a twisted adnexal tumor were retrospectively evaluated. RESULTS The most common findings on MR images were nonspecific: deviation of the uterus to the twisted side (n = 9), engorged blood vessels on the twisted side (n = 6), a small amount of ascites (n = 5), and obliteration of fat (n = 4). The following characteristics were seen only in the five patients with hemorrhagic infarction: (a) a protrusion of the lesion on the twisted side to which the uterus was continuous or engorged blood vessels converged (n = 5); (b) thick, straight blood vessels that draped around the lesion (n = 2); (c) distinct hematoma (n = 2); and (d) complete absence of enhancement (n = 3). CONCLUSION: Three findings (it, b, and d) seem to be diagnostic of the twisted adnexal tumor and may facilitate prompt surgical intervention at examination with MR imaging or CT.