Abstract: Objective: To explore the clinical significance of the telomerase activity in the induced sputum of lung cancer patients and to search for a newmeans of clinical diagnosis for lung cancer. Methods: The telomerase activity in the induced sputa and spontaneous sputa from 30 patients with lung cancer and 15 patients with benign lung disease pathologically confirmed was determined using TRAP-PCR-ELISA. Results: The positive rate in the induced and spontaneous sputum from lung cancer patients and spontaneous sputum from benign lung disease patients were 80%, 56.7%, and 13.3%, respectively, while the OD value of telomerase activity was 0.523±0.267, 0.349±0.247, and 0.091±0.110, respectively. The positive rate and OD level in induced sputum from the patients with lung cancer were significantly higher than that of the other 2 control groups (P<0.01). Conclusion: Detection of telomerase activity in the induced sputum may be helpful in the diagnosis of lung cancer and differential diagnosis with other benign lung diseases and can be more accurate than using spontaneous sputum.