During recent years the BTA-TRAK-assay (Bard Diagnostics, Redmont, USA) has been described in several investigations to be of clinical utility for patients suffering from bladder cancer. In a prospective study we investigated over four months the voided urine samples of all consecutive patients undergoing cystoscopy independent of their clinical background (n = 244) with the BTA-TRAK-assay. With a specificity of 95% for benign urological diseases (cut off: 1300 U/mL) we found a sensitivity of 13% for active bladder tumours. Using healthy individuals as a reference group (cut off: 40 U/mL) we found a sensitivity of 56% (specificity 67%). Using the cut off value recommended by the manufacturer (14 U/mL) a specificity of 54% and a sensitivity of 62% was found. For patients without relapse (NED) versus patients with active bladder tumours we got a specificity of 55% and a sensitivity of 62%. Due to an insufficient specificity and sensitivity the BTA-TRAK-test is not able to replace cystoscopy nor to improve existing diagnostic strategies in bladder cancer.