The diagnosis of bladder cancer is confirmed by histological analysis of tissue biopsies. Cytology of urine samples is a noninvasive alternative. The aim of this work was to find out whether flow cytometry of urine samples is more sensitive than cytology. For this purpose we studied 115 patients suspected of having bladder cancer. Cells isolated from urine samples were analyzed by cytometry for the expression of cytokeratin and CD 45 and for DNA measurements such as: DNA index, synthesis phase fraction and proliferative index (SPF + G2/M phase). At the same time we carried out cytological analysis. All positive cases were confirmed by histology (21/115), 18 were diagnosed by flow cytometry and 16 by cytology, with a sensitivity of 85.7% and 76.1%, respectively. Two cases were found to be positive by flow cytometry, which were not confirmed by histology, while no false positives were detected by cytology. We found that both techniques gave almost identical results for the diagnosis of bladder cancer, although there were differences in non-malignant samples. In conclusion, flow cytometry is slightly more sensitive than cytology but the combination of the two techniques improves the diagnosis.