Successful management of transitional-cell carcinoma of the urinary bladder is greatly dependent upon regular surveillance and early detection of persistent or recurrent carcinoma. The development of a highly sensitive urinary test for the detection of transitional-cell carcinoma of the bladder could have a dramatic impact on our ability to diagnose and monitor bladder cancer patients as well as influence the treatment outcome. The urinary level of the nuclear matrix protein, NMP22, has been found to be elevated in patients with urothelial malignancy. This has prompted the development of an immunoassay to quantitate urinary NMP22 and use it as a cancer-specific marker. We provide a summary of the studies completed with the immunoassay for urinary NMP22 as an indicator for the presence of transitional-cell carcinoma and compare the results with those obtained using other screening modalities.