PURPOSE: To evaluate the radioloic findings of malignant retroperitoneal fibrosis. MATERIALS AND METHODS: Post-contrast CT (n=9) and urographic (n=7) findings of nine patients with malignant retroperitoneal fibrosis were retrospectively analyzed. Primary tumors were found to be advanced gastric cancer (n=6), early gastric cancer (n=1), breast cancer (n=1), and cervical cancer (n=1). We analyzed CT findings with regard to the site of soft tissue lesion, ureteral involvement, the presence or absence of hydronephrosis, and distant metastasis. The level and length of ureteral involvement, presence or abscence of ureteral stenosis, and ureteral displacement as seen on urography, were analyzed. RESULTS: On CT scans, enhanced soft tissue lesions (mass, 5 cases; plaque, 4 cases) encircling the abdominal aorta and IVC were noted in all cases. Thickening of the ureteral wall (n=8), hydronephrosis (n=9), and enlarged lymph node (n=5) were also seen. On urography, irregular stenosis and medial displacement of ureters from level L2 to S2 were noted in all cases. The length of ureteral involvement was 4-6.5cm. CONCLUSION: The common CT findings of malignant retroperitoneal fibrosis were enhanced soft tissue lesion encircling the abdominal aorta and IVC, hydronephrosis, and thickening of the ureteral wall. On urography, ureteral stenosis and medial displacement were seen.