In a preoperative study to identify accurately metastases to the lymph nodes within the pelvis and retroperitoneum, the three imaging techniques of pelvic interstitial lymphoscintigraphy, bipedal lymphangiography and computer tomography (CT) scanning were compared in 69 patients with carcinoma of the cervix uteri or rectum. Results were correlated with histologic node examination in all patients and each technique was assessed for sensitivity, specificity and over-all accuracy. Lymphoscintigraphy is too unreliable for routine use in the diagnosis or staging of pelvic malignant conditions. Lymphangiography detects involved lateral pelvic and para-aortic nodes but is unable to visualize the internal iliac or other medial pelvic nodes. CT scanning is only accurate if metastatic nodes are enlarged but may reveal other pathways of spread which will alter the surgical approach.