It has recently been shown that allelic abnormalities, detected by microsatellite analysis of the DNA extracted from urine sediment, can be successfully used for the detection of transitional cell carcinoma (TCC) of the bladder. The diagnostic accuracy of urinary cytology, urinary bladder cancer (UBC) marker, bladder tumor antigen (BTA) and microsatellite sequence alterations was compared in 42 patients who were recruited for the study. Of them, 30 had been diagnosed with TCC at cystoscopy plus biopsy (group A). Seven patients without any apparent lesions after trans-urethral resection (TUR) and 6 subsequent weeks of endovesical administration of bacillus Calmette-Guerin (BCG), had irritative symptoms. None of them had positive cytology or TCC bladder mucosa biopsies (group B). In the control group were 5 other subjects who were affected by benign prostatic hypertrophy and candidates for prostatectomy (group C). Urine and blood samples were obtained from all of the patients before surgery. Tumor tissue and normal mucosa samples were taken from groups A and C during surgery. Different urinary sediment analyses were performed by using both nuclear medicine and molecular tests. UBC and BTA-t analyses were carried out using monoclonal antibody tests while microsatellite analyses were performed using extracted DNA and electrophoresis of polymerase chain reaction (PCR) products on 13 different primers. Urinary cytological examinations were carried out using the Autocyte Preparation System(R). Urinary cytology confirmed the presence of TCC in 13.3% of patients. The BTA-t marker allowed the identification of 73.3% of cancers with 50% specificity; the UBC marker identified 63.3% of the cases with 41.6% specificity. Microsatellite analysis permitted the identification of 83.3% of the tumors with 100% specificity. DNA analysis demonstrated high sensitivity in patients affected by superficial (81.4%) or G1 (80%) tumors, even when cytological studies demonstrated little or no sensitivity. Microsatellite analysis is a highly-sensitive and specific marker for TCC diagnosis and its monitoring, especially in patients with low-stage and low-grade tumors. Other testing procedures failed to increase urinary cytological diagnostic significance.