Human telomerase reverse transcriptase (hTERT) has been identified as the catalytic subunit of human telomerase. To clarify the clinical significance of hTERT mRNA in hepatocellular carcinoma (HCC), we investigated the relationship between telomerase activity and hTERT mRNA in human HCC and non-HCC tissues. The hTERT mRNA was detected in 17 (89.47%) of 19 livers with HCC and in 4 (21.05%) of 19 noncancerous tissues from these livers. Telomerase activity was detected in 17 of the 19 tumor tissues (89.47%) and in 4 of the 19 nontumor tissues (21.05%). The hTERT mRNA was detected in all tissues that were telomerase-positive and it was undetected in all tissues that were telomerase-negative. The correlation between the expression of hTERT mRNA and human telomerase activity in this study indicates that hTERT mRNA could be useful to diagnose cancer. Also, as telomerase production may be under the control of hTERT mRNA, the possibility is great that noncancerous liver tissue with chronic liver diseases acquires HCC when the hTERT mRNA is positive.