Surgical resection is so far the most reliable therapy for localized non-small-cell lung cancer (NSCLC). Although the combination of several modalities such as chemotherapy or radiotherapy is used to treat advanced or recurrent disease, the results have not been satisfactory. A new therapeutic strategy is thus required to improve lung cancer treatment. Gene therapy is one such new therapeutic strategy. Several clinical trials of gene therapy protocols have been conducted and patient eligibility and being efficacy are evaluated. Representative studies of gene therapy for lung cancer and an interim report on a clinical trial using adenovirus vector expressing wild-type p53 in non-small cell lung cancer in Japan are introduced in this paper. Problems encountered and future regimens are also discussed.