Cytologic evaluation of the urinary tract can be diagnostically rewarding in cases of renomegaly or when discrete kidney or bladder masses are identified. Cytology can often help to distinguish between cystic, inflammatory, and neoplastic disorders. Various types of cystic and benign urinary tract lesions, diseases associated with urinary tract inflammation, and the cytologic differences between primary and metastatic neoplasms of the kidney and bladder are described. Basic sampling techniques for urinary tract cytology are also discussed.