Infusion excretory urography not only clearly delineates the urinary tract structures, but provides additional information about the type of pelvic mass present. Benign uterine fibroids show contrast enhancement in a significant number of cases, whereas endometrial and cervial malignancies give no specific pattern. Cystic and mixed ovarian neoplasms show rim opacification in over 50 per cent of cases, and the presence of this rim sign points strongly to an ovarian lesion. The opacification of solid ovarian tumors cannot be differentiated from that of uterine fibroids unless other identifying features such as specific calcification or visualization of a normal uterus are present. Pelvic inflammatory disease shows no specific type of opacification. Excretory urography is part of the preoperative evaluation in most patients with pelvic mass lesions. By utilizing the infusion method, high quality excretory urograms are obtained, and, in addition, helpful information is obtained regarding the type of pelvic mass present.