Telomerase is a ribonucleoprotein enzyme that synthesizes telomeric repeats onto chromosomal ends using a segment of its RNA component as a template. Its activity has become an established indicator of the diagnosis, biological behavior, and prognosis of several tumors. However, few studies have investigated the diagnostic and prognostic importance of the expression of telomerase catalytic subunit (hTERT) mRNA in transitional cell carcinoma of the upper urinary tract (TCC-UUT). We investigated the expression of hTERT mRNA using in situ hybridization in 125 cases of TCC-UUT, and also its relation with the expression of telomerase RNA component (hTERC), proliferating cell nuclear antigen (PCNA) immunoreactivity, clinicopathologic parameters, and clinical outcome. A positive expression of hTERT mRNA was recognized in 93.6% of the samples and was apparent within the cytoplasm of tumor cells. In the normal urothelium examined in a few cases, its expression was barely detected. hTERT mRNA scores showed a significant association with hTERC score. However, no relationship was found between the expression of hTERT mRNA and clinicopathologic findings, PCNA index, or prognosis. These results suggest that the expression of hTERT mRNA does not predict prognosis in TCC-UUT.