A novel closed-tube format telomeric repeat amplification protocol specifically adapted to real-time detection and quantification of telomerase activity was developed. The assay utilizes energy transfer primers, which emit fluorescence only upon incorporation into polymerase chain reaction (PCR) amplification products. The assay, performed on a real-time detection instrument, is highly reproducible, sensitive, and specific. Telomerase activity in as few as 10 cultured cells can be quantified with a linear dynamic range more than 2.5 logs. In addition, the presence of potential PCR inhibitor(s) is readily detectable by inclusion of an internal PCR control labeled with a second color fluorescence.