99mTc-pyrophosphate and 99mTc-diphosphonate have successfully been employed In the diagnosis of neoplastic pelvic disease in women. In our ongoing study, 48 women with pelvic masses, underwent dynamic pelvic scintigraphy, correlative ultrasonography and exploratory laparotomy. Dynamic scintigraphy and region of interest time/activity curves generated from computerized data acquisition have proven effective in the differential diagnosis of uterine leiomyomas from ovarian cysts. In a group of 24 women whose scintigraphic data were consistent with our criteria for uterine leiomyoma, 21 were confirmed histologically. Of 30 women, 29 were accurately diagnosed on scintigraphy as having an ovarian cyst and two patients with coexisting ovarian cysts and uterine fibroids were both correctly diagnosed prior to surgery. Detected lesions ranged from 6-22 cm in diameter. Our findings support the use of dynamic pelvic scintigraphy for differentiating uterine leiomyomas from ovarian cyst.