Telomerase, a ribonucleoprotein enzyme required for maintenance of telomere length, is implicated in aging and cancer. It is silent in the majority of human normal cells due to a tight repression of its catalytic component hTERT (telomerase reverse transcriptase) gene. Activation of telomerase by induction of hTERT expression has been shown to be a prerequisite step in cellular immortalization and malignant transformation. I study the mechanism(s) that control the regulated switch between repression and activation of the hTERT gene or telomerase in normal and malignant human cells, with special interest in the role of epigenetic factors. The obtained results are believed to contribute to rational development of the anti-aging/cancer strategy by manipulating telomerase expression.