To evaluate the expression and clinical significance of urinary nuclear matrix protein (NMP22) and cytokeratin 18 (CK18) for transitional cell carcinoma of the bladder.Urinary NMP22 and CK18 levels of 293 patients with transitional cell carcinoma of the bladder, 400 patients with non-transitional cell carcinoma of the bladder, and 105 bladder benign disease were analysed by enzyme-linked-immunosorbent assay (ELISA).The levels of urinary NMP22 and CK18 in the patients with transitional cell carcinoma of the bladder (M = 17.3 U/ml, M(CK18) = 484.2 U/L) were significantly higher than those in the non-transitional cell carcinoma of the bladder (M = 6.8 U/ml, M(CK18) = 156.0 U/L) and the benign disease group (M(NMP22) = 2.3 U/ml, M(CK18) = 66.6 U/L) (P < 0.001). The sensitivity and specificity of urinary NMP22 and CK18 were 79.2%, 88.6% and 78.2%, 82.9%, respectively, for transitional cell carcinoma of the bladder before any treatment. The joint sensitivity of the two markers was 91.7%. The NMP22 and CK18 levels were significantly lower in the recovered patients after surgical operation (P < 0.01), while in patients with recurrence or metastasis the levels of the markers were significantly higher (P < 0.01). There was a significant relationship between NMP22 and CK18, (r = 0.689, P < 0.01). The levels of urinary nmp22 and CK18 were significantly different among pathological grade G1, G2, G3, and stage Ta, T1, T2, T3 (P < 0.01).NMP22 and CK18 are useful tumor marker for diagnosis of transitional cell carcinoma of the bladder and for monitoring the state of illness. The joint use of the two markers can improve the sensitivity of cancer detection. NMP22 and CK18 may become a new class of tumor markers, and to be the basis for development of a new assay with an increased efficacy for the detection and treatment of bladder cancer.