We prospectively evaluated the performance of urinary NMP22 test in the detection of transitional carcinoma (TCC) of the bladder. Urine samples were obtained from 39 patients with known bladder cancer, 37 patients with primary hematuria. 18 with benign urological conditions and 20 healthy subjects. Overall sensitivity and specificity of NMP22 with reference value of 10 U/ml was 72 and 73%, respectively. Sensitivity for pT1 and pT2 tumors was 83%, whereas that for pTa tumors was 55%. When the test was determined before and after transurethral resection (TUR) of bladder tumor, it was shown that the TUR effected the NMP22 level. Urinary NMP22 was highly sensitive for high-risk bladder cancer. However, the sensitivity of the test is somewhat lower in low grade and stage tumors. Additionally, the effect of previous resection limits its value in the follow up of patients with superficial tumors. The larger series with longer follow up may lead us to determine the time to neglect the effect of TUR on NMP22 and the test kit should be upgraded by the manufacturer to exclude the false positive results due to inflammatory conditions.