A case of hyperkeratotic squamous epithelium of the distal renal pelvis and ureter, clinically identifiable as leukoplakia, is reported in a solitary kidney. Because of the need to conserve renal parenchyma in this patient, the lesion was treated conservatively at operation after careful exploration and full thickness biopsy failed to reveal malignancy. Close monitoring of this potentially premalignant lesion has documented no progression at twenty-five months.