A remarkable volume of novel findings on the oncogenesis of cancer has been presented during the past decade, including the recognition of tumor suppressor genes, Rb and p53. In the field of molecular biology of the lung carcinogenesis, however, the study of the molecular events occurring during the progression from premalignant changes to invasive lung cancer, has been hampered by a number of difficulties. First, lung cancer includes different phenotypes: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), which contains three different main types: adenocarcinoma, squamous cell carcinoma and large cell carcinoma. The development of these phenotypes of lung cancer may involve different molecular mechanisms. Second, the specific familial genetic changes of lung cancer are largely unknown. Third, the early detection of lung cancer is difficult. In this article, we review recent topics in the field of molecular oncology of the lung. We will also refer to our novel detection systems for mutations in the cells in the tissue specimens. While specific oncogenesis of lung cancer phenotypes might eventually become evident, and successful gene-therapy might be carried out according to newly established molecular technology in the near future, we should attempt to evaluate the independent multi-steps of oncogenesis in each lung cancer patient.