Lung cancer continues to be the leading cause of cancer deaths worldwide. Cigarette smoking is the predominant cause of lung cancer. Researchers found that tobacco-induced molecular changes in the oral epithelium are similar to those in the lung epithelium. Furthermore, there has been considerable progress in investigating the tumorigenesis of oral epithelium using molecular markers. These results offer hope that we can predict lung cancer in smokers by oral examination, which is much easier and more practical than lung biopsy. The hypothesis is to collect oral epithelial cells by gently scraping the oral mucosa, and analyze the DNA variation in these cells using molecular biological methods. Therefore, the oral epithelium is serving as a surrogate tissue for assessing smoking-induced molecular damage to the lungs and thus have important implications for early detection of lung cancer. (C) 2009 Elsevier Ltd. All rights reserved.