Objectives: To evaluate the pathologic findings and outcomes after distal ureterectomy for a retained ureteral segment following incomplete nephroureterectomy for urothelial carcinoma of the renal pelvis or ureter. Materials and Methods: After IRB approval, an institutional database identified patients who underwent distal ureterectomy for a retained ureteral segment after assumed complete nephroureterectomy for urothelial carcinoma of the upper ureter or renal pelvis. Clinical and pathologic variables were analyzed. Results: From January 1993 to July 2007, 12 patients were identified with median age at the time of ureterectomy of 60.5 years (41-85 years). Initial approach to surgery was open in 9 patients and laparoscopic in 3 patients. The median time from nephroureterectomy to distal ureterectomy was 23.5 months (range 2-66). At the time of initial surgery, pathologic stage was Ta, T1, T2, and T3 in 3,4,1, and 4 patients respectively. Initial pathology was urothelial carcinoma; grade 2 in 6 patients and grade 3 in six patients. Pathology from the subsequent surgery demonstrated urothelial carcinoma in the retained ureteral segment in 8 patients, dysplasia or atypia in 3 patients, and 1 patient with chronic inflammation. Local recurrence in 2 patients was present in a segment of ureter discontinuous with the bladder after laparoscopic nephroureterectomy. Three patients (25%), all with initial grade 3 renal pelvis lesions, developed metastatic disease. Conclusions: Tumor recurrence in a retained ureteral segment after incomplete nephroureterectomy is a significant problem and may contribute to intravesical recurrence or metastatic disease. Complete, en bloc resection is imperative to minimize these risks.