Purpose: Although rarely indicated, surgical treatment of severe megaureter can pose a formidable technical challenge, especially in the small infant. We present our experience and outcomes with end cutaneous ureterostomy as a temporizing adjunct to future ureteral reimplantation. Materials and Methods: We performed a retrospective cohort study of patients who underwent end cutaneous ureterostomy between 1993 and 2005. Patient demographics, surgical details and outcomes were recorded. Results: A total of 29 patients (22 males, 7 females) underwent diversion of 34 renal units. Primary megaureter was diagnosed in 15 patients (17 renal units). Secondary megaureter was found in 10 patients (12 renal units). Postoperative megaureter was diagnosed in 4 patients (5 renal units). Mean patient age at time of diversion was 3.2 months for those with primary megaureter and 1.4 years overall. Bilateral diversion or diversion of a solitary functioning kidney was performed in 14 patients (48%), of whom 4 had renal insufficiency. Nine patients (31%) had a febrile urinary tract infection while awaiting undiversion, with no evidence of renal scarring on followup. Undiversion was performed in 12 patients (13 renal units) with primary megaureter at a mean age of 18 months. Overall, undiversion was performed in 21 patients (23 renal units), and ureteral tailoring was required in only 5 renal units (22%). Mean followup after undiversion was 4.2 years for primary megaureter and 3.9 years overall. Conclusions: End cutaneous ureterostomy is a safe and effective procedure to temporize massive hydronephrosis while awaiting definitive ureteral reimplantation. © 2007 American Urological Association.