Studies using the telomeric repeat amplification protocol (TRAP) assay have demonstrated telomerase activity not only in cancers but also in non-cancerous lesions. However, quantitative differences in activity between both lesions have not been examined. In the present study, using a stretch PCR assay, telomerase activity was analyzed quantitatively in cervical cancer, its precursor squamous intra-epithelial lesions (SILs) and normal cervix. In stretch PCR assay, telomerase activity was expressed in relative units vs. control activity from C33A cells (100 units). Mean telomerase activities in cervical cancer, SIL and normal cervix were 72+/-35 units, 18+/-17 units and 7+/-4 units, respectively, suggesting that telomerase activity in cancer lesions was quantitatively distinct from that in pre-malignant lesions, which may mean a much more pronounced activation of telomerase in cancers than in SIL. Our findings also suggest that stretch PCR assay can distinguish telomerase activity in cancer from that in non-cancerous lesions and may be useful for the differential diagnosis of cancer lesions.