Abstract: Objective:This study investigated the positive detection rate of cytoplasm thymidine kinase1 (TK 1) in lung cancer patients and the relationship of TK1 with clinicopathological features and prognosis. Methods: Sensitive chemiluminescence dot-blot assay was used to detect serum TK 1 levels in 73 lung cancer patients and 56 normal control subjects.Results:The positive detection rate of TK 1 was elevated in the lung cancer patients compared with the controls ( P=0.006). The positive detection rate of TK 1 was also correlated with distant metastases, but not with other factors, such as smoking, sex, lymph node metastasis, and pathology types. The 2 year survival of the patients with negative TK 1 detection was significantly longer than that of the patients positively detected with the marker ( P<0.001). Conclusion: Serum TK1, a new tumor marker, has potential applications in the diagnosis and prognosis of lung cancer.