Pathologic examination of urinary specimens is increasingly recognized as an essential component of detection and monitoring for patients with bladder neoplasms. Among the available techniques, urinary cytology is the most useful. The current status of urinary cytology can be summarized as follows: 1. The demand for urinary cytology is steadily increasing as clinicians have realized the limitations of cystoscopy and even biopsy for monitoring bladder cancer patients, especially those having carcinoma in situ or receiving topical therapy. 2. Urinary cytology is currently an essential procedure for monitoring all patients with urothelial neoplasms and, if consistently used, can actually decrease the frequency with which patients need to be subjected to cystoscopy. 3. Even in moderately experienced hands, urinary cytology can detect almost all high-grade urothelial neoplasms. 4. The cytologic interpretation of low-grade transitional cell neoplasia requires expertise. These cells lack many of the features of malignancy, a source of confusion for the diagnostician but a positive factor for the patient since neoplasms composed of these cells are almost never aggressive. 5. The most useful type of urinary specimen for routine diagnostic interpretation is freshly voided, randomly collected urine. Catheterized specimens and bladder washings may yield more and better preserved cells, but no patient should be catheterized solely to obtain diagnostic material. 6. Preservation of urinary specimens in alcohols is not necessary unless prolonged storage is contemplated. Refrigeration to prevent bacterial growth and inhibit further cellular degeneration is required, however. 7. Cytologic details are best displayed with membrane filtration but other types of processing are adequate. The computer-programmed cytocentrifuge is currently most popular. 8. Optimal recognition of cytologic details requires some form of Papanicolaou staining; Romanovsky dyes are less desirable. 9. Urothelial cells with nuclear:cytoplasmic ratios of 1:2 or less should not be interpreted as malignant regardless of the degree of anaplasia of their nuclei. 10. Papillary aggregation is not a reliable feature of low-grade neoplasia in urinary samples. 11. Using appropriate criteria, the differential diagnosis of urothelial neoplasia versus the reactive/regenerative/reparative changes secondary to urinary stones can almost always be accomplished. 12. Alkylating agents such as Cytoxan, thio-TEPA, and mitomycin C produce characteristic but nonspecific changes in urothelial cells. These changes rarely mimic those of carcinoma. The diagnosis of urothelial neoplasia need not be confounded by previous treatment. 13. Flow cytometry and digitized image analysis are currently used for diagnostic interpretations of urinary specimens in selected centers. Their routine use must await further refinements in instrumentation and the formulation of more searching questions.