Using scanning electron microscopy (SEM), differences in cell surface morphology are identifiable between normal urothelium and malignant urothelia including the presence of pleomorphic microvilli (PMV). PMV have been reported in carcinomas of the urinary bladder, and they appear early in the pathogenesis of these tumors in animal models. Preliminary studies in our laboratory and others' demonstrated similar changes in tissue and cytologic specimens from patients with bladder cancer. We observed and evaluated normal and neoplastic cells of the human bladder by SEM in a preliminary assessment of surface topography with regard to tumor growth, grade, and stage. However, while these SEM observations indicated that differences between normal and abnormal urothelia could be readily recognized, the distinction between the various types of atypical cells was not as clearly defined. Data collected so far indicates that changes in the surface topography of the exfoliated cells may possibly vary both in relation to tumor grade and stage. Based on these qualitative observations, we expanded our approach by using a computerized image analysis system directly interfaced with the SEM. The measurements which can be made include cell surface area, diameter, length, width, perimeter, orientation and number of PMV per unit area. Statistical analysis is also performed. The boundaries between cells are not recognizable by the system, making the single cells present in cytologic specimens ideal for evaluation. Uniform short microvilli are readily distinguished from PMV. Preliminary evaluation of 23 patients has distinguished specimens from malignant cases compared to patients with benign lesions.