Telomerase, an intranuclear enzyme, binds to telomeres at chromosome ends, helps to elongate telomere length and is closely linked to attainment of cellular immortality, a step in carcinogenesis. Since telomerase activity has been detected in several human tumors and hematopoietic malignancies, this enzyme is thought to be a useful marker for cancer diagnosis. Among the components of telomerase, human telomerase catalytic subunit(hTERT) is the most important regulatory factor for telomerase activity. Therefore, quantitation of hTERT mRNA expression may be a new approach to measuring telomerase activity.