Abstract: Abstract　Objective: To detect the methylation status of the retinoic acid receptor-β ( RAR-β ) gene in the plasma and tissues of non-small cell lung cancer (NSCLC) patients and to evaluate its clinical significance in screening and early diagnosis of NSCLC. Methods: A total of 120 NSCLC patients were enrolled, and nested methylation-specific polymerase chain reaction ( nMSP ) was used to determine the methylation of the RAR-β gene in the DNA of the lung cancer cells, paraneoplastic tissues, and plasma from peripheral blood. The determination was also conducted on 120 normal blood samples. The results of the groups were compared. Results: The total frequency of the RAR-β methylation was 59.2% in lung cancer tissues, which was significantly higher than that in the nonmalignant tissues at 17.5% ( P < 0.001 ). The detection rate of hypermethylation for RAR-β gene was 27.5% in the plasma of the 120 NSCLC cases, and no methylated RAR-β gene was found in the plasma of the control group ( P < 0.001 ). There were significant differences in the detection rate of the methylation of RAR-β gene between the lung cancer tissues and the plasma of NSCLC patients ( P < 0.001 ). The detection rate of hypermethylation in the plasma did not significantly correlate with the clinical classification, the pathologic types, and clinical staging of the NSCLC. Conclusion: Detection of RAR-β gene methylation in the plasma of NSCLC patients using nMSP might provide valuable information for early screening and diagnosis of the NSCLC.