BACKGROUND Telomerase in an enzyme ribonucleoprotein responsible for cell immortality and oncogenesis. Telomerase activity has been detected in most cancers, including prostate cancer. To verify whether the detection of telomerase in prostate needle biopsy samples could have diagnostic value, we blindly assayed telomerase activity in samples from patients who were clinically suspected of having prostate cancer. METHODS A total of 183 prostate biopsy samples was obtained from 63 patients who were suspected of having prostate cancer. Telomerase activity was determined by polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) assay. An internal telomerase assay standard (ITAS) was used in this study to distinguish false negatives. RESULTS Telomerase activity was detected in 17 of 19 (89.5%) patients with prostate cancer (chi(2) test, P < 0.005). In 39 of 42 (92.9%) biopsy samples from these 19 prostate cancer patients, confirmed histologically as prostate cancer, telomerase activity (chi(2) test, P < 0.005) was detected. Meanwhile, we also found one false-positive sample. In contrast, all of 44 normal or benign prostate disease patients (124 biopsy specimens) were telomerase-negative. We also revealed that poorly differentiated prostate cancer often expresses a high level of telomerase activity. The area of cancer tissue in biopsy specimens was not associated with relative telomerase activity. CONCLUSIONS This study suggests that determination of telomerase activity in prostate needle-biopsy samples might be a useful tool for detecting prostate cancer.