Abstract: Objectivc To investigate the possible relations hip between telomerase expression and progression of lung cancer. Methods The techniques of TRAP-PCR-ELISA and TRAP-silver stain i ng were employed to detecte telomerase activity in 24 fresh primary lung cance r tissues and 6 benign lung lesions obtained by surgical resection.Resul ts The levels of telomerase activity in primary lung cancer tissues was si gnificantly higher than that in benign lung lesions.Positive rate of telomerase activity detection in lung cancer patients was 75%.The level of telomerase acti v ity in squamous cell carcinomas was significantly higher than that in adenocarc i nomas.The positive rate of telomerase activity was 50% in stage Ⅱ，92.3% in st age Ⅲ.The difference between them was not significant. Conclusion Telomerase expression might contribute to the progres sion of lung cancer and could be used as a tumor marker in the diagnosis of lung cancer.