We present a case of multilocular cystic nephroma with an unusual localization treated by a nephron-sparing procedure. A 21-year-old white woman presented with a history of hematuria and right lumbar pain. Imaging techniques revealed a multilocular cystic mass originating from the renal parenchyma but mainly involving the renal pelvis. The lesion was localized almost entirely within the renal pelvis at surgery and was treated by excision. Pathologic analysis was consistent with multilocular cystic nephroma. The patient remains free of recurrence with 10 years of follow-up. We conclude that multilocular cystic nephroma may present as a cystic lesion localized within the renal pelvis, and we advocate simple excision of these lesions. (C) 1998, Elsevier Science Inc. All rights reserved.