21 CT examinations were performed in 19 patients who had undergone previous nephrectomy for renal carcinoma or retroperitoneal malignancy. 9 patients were free of disease and 10 had recurrence. Findings of recurrent disease included masses in the vacant renal fossa, inability to visualize the inferior vena cava or aorta, and ipsilateral psoas muscle thickening. Possible pitfalls in diagnosis are discussed.